Graphic summary
  • Show / hide key
  • Information


Scientific and technological production
  •  

1 to 50 of 308 results
  • Optimization of laser processes for local rear contacting of passivated silicon solar cells

     Colina Brito, Monica Alejandra; Martin Garcia, Isidro; Voz Sanchez, Cristobal; Morales Vilches, Ana Belen; Ortega Villasclaras, Pablo Rafael; Lopez Rodriguez, Gema; Garcia Molina, Francisco Miguel; Alcubilla Gonzalez, Ramon
    Energy procedia
    Date of publication: 2014-01-31
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Laser Firing Contact (LFC) and Laser Doping (LD) have become potential alternatives to the Al BSF thermal processing conventionally used in p-type c-Si solar cell rear contacts. Optimized LFC and LD processes allow, not only the generation of efficient micro-contacts, but also the diffusion of p-type doping impurities reducing the surface recombination velocity due to the formation of a local back surface field (BSF). In this work, three different laser strategies to create ohmic micro-contacts are studied: 1) evaporated Aluminum LFC, 2) Aluminum foil LFC and 3) Aluminum oxide (Al2O3) LD. The laser source used was a pulsed Nd-YAG 1064 nm laser working in the nanosecond regime. Laser parameters were explored to optimize the electrical behavior of the contacts and their carrier recombination rate. Optimized laser parameters lead to specific contact resistance in the 1.0 1.3 m¿¿cm2 range for all three strategies. From the point of view of carrier recombination, better results were obtained for Al2O3 LD, probably related to the lower energy pulse needed to create the contact. Next, the three proposed laser approaches were applied to the back surface of heterojunction silicon solar cells. Contact quality was not limiting any cell performance indicating that the contact quality is good enough to be applied in high-efficiency c-Si cell concepts. On the other hand, surface recombination velocity at the rear surface on the final devices also points out to Al2O3 LD as the best alternative.

  • Restraints in low dimensional organic semiconductor devices at high current densities

     Pfattner, Raphael; Moreno Sierra, Cesar; Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon; Rovira, Concepció; Puigdollers Gonzalez, Joaquin; Mas Torrent, Marta
    Organic electronics
    Date of publication: 2014-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The understanding of the charge carrier transport in electronic materials is of crucial interest for the design of efficient devices including especially the restraints that arise from device miniaturization. In this work the performance of organic thin-film and single crystal field-effect transistors with the same active material was studied in detail focusing on the high current density regime, where a pronounced non-hysteretic maximum in the transconductance was found. Interestingly, in this operation mode for both, thin films and single crystals, comparable densities of free and gate-induced charge carriers were estimated. Kelvin probe microscopy was used to measure the contact potential difference and the electrical field along the transistor channel during device operation exhibiting the formation of local space charges in the high current density regime. © 2013 Elsevier B.V. All rights reserved.

  • Recovery of indium-tin-oxide/silicon heterojunction solar cells by thermal annealing

     Morales Vilches, Ana Belen; Voz Sanchez, Cristobal; Colina Brito, Monica Alejandra; Lopez Rodriguez, Gema; Martin Garcia, Isidro; Ortega Villasclaras, Pablo Rafael; Orpella Garcia, Alberto; Alcubilla Gonzalez, Ramon
    Energy procedia
    Date of publication: 2014-01-31
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The emitter of silicon heterojunction solar cells consists of very thin hydrogenated amorphous silicon layers deposited at low temperature. The high sheet resistance of this type of emitter requires a transparent conductive oxide layer, which also acts as an effective antireflection coating. The deposition of this front electrode, typically by Sputtering, involves a relatively high energy ion bombardment at the surface that could degrade the emitter quality. The work function of the transparent conductive oxide layer could also significantly modify the band structure at the emitter. In this work, we study the particular case of p-type crystalline silicon substrates with a stack of n-doped and intrinsic amorphous silicon layers deposited by Plasma-Enhanced Chemical Vapor Deposition. The front electrode was an indium-tin-oxide layer deposited by Sputtering. The Quasi-Steady- State Photoconductance technique has been used to characterize the emitter quality by measuring the effective lifetime and the implicit open-circuit voltage. These measurements confirmed a strong degradation of the heterojunction after depositing the indium-tin-oxide layer. However, it is also shown that the initial degradation could be completely recovered by an adequate thermal treatment. In this sense, annealing times from 10 to 90 minutes at temperatures ranging from 100 to 160 °C have been studied, both in vacuum and inside an oven.

  • Compositional influence on the electrical performance of zinc indium tin oxide transparent thin-film transistors

     Marsal Vinade, Albert; Carreras Seguí, Paz; Puigdollers Gonzalez, Joaquin; Voz Sanchez, Cristobal; Galindo Lorente, Sergi; Alcubilla Gonzalez, Ramon; Bertomeu Balaguero, Joan; Antony, Aldrin
    Thin solid films
    Date of publication: 2014-03-31
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this work, zinc indium tin oxide layers with different compositions are used as the active layer of thin film transistors. This multicomponent transparent conductive oxide is gaining great interest due to its reduced content of the scarce indium element. Experimental data indicate that the incorporation of zinc promotes the creation of oxygen vacancies, which results in a higher free carrier density. In thin-film transistors this effect leads to a higher off current and threshold voltage values. The field-effect mobility is also strongly degraded, probably due to coulomb scattering by ionized defects. A post deposition annealing in air reduces the density of oxygen vacancies and improves the field-effect mobility by orders of magnitude. Finally, the electrical characteristics of the fabricated thin-film transistors have been analyzed to estimate the density of states in the gap of the active layers. These measurements reveal a clear peak located at 0.3 eV from the conduction band edge that could be attributed to oxygen vacancies. (C) 2013 Elsevier B.V. All rights reserved.

  • Numerical simulations of rear point-contacted solar cells pn 2.2 Wcm p-type c-Si substrates

     Lopez Gonzalez, Juan Miguel; Martin Garcia, Isidro; Ortega Villasclaras, Pablo Rafael; Orpella Garcia, Alberto; Alcubilla Gonzalez, Ramon
    Progress in photovoltaics
    Date of publication: 2013-07
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Rear surface of high-efficiency crystalline silicon solar cells is based on a combination of dielectric passivation and point-like contacts. In this work, we develop a 3D model for these devices based on 2.2¿Ocm p-type crystalline silicon substrates. We validate the model by comparison with experimental results allowing us to determine an optimum design for the rear pattern. Additionally, the 3D model results are compared with the ones deduced from a simpler and widely used 1D model. Although the maximum efficiency predicted by both models is approximately the same, large deviations are observed in open-circuit voltage and fill factor. 1D simulations overestimate open-circuit voltage because Dember and electrochemical potential drops are not taken into account. On the contrary, fill factor is underestimated because of higher ohmic losses along the base when 1D analytical model is used. These deviations are larger for relatively low-doped substrates, as the ones used in the experimental samples reported hereby, and poor passivated contacts. As a result, 1D models could mislead to too short optimum rear contact spacing.

  • Access to the full text
    ¿Silicon millefeuille¿ : From a silicon wafer to multiple thin crystalline films in a single step  Open access

     Hernández García, David; Todorov Trifonov, Trifon; Garin Escriva, Moises; Alcubilla Gonzalez, Ramon
    Applied physics letters
    Date of publication: 2013-04-29
    Journal article

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    During the last years, many techniques have been developed to obtain thin crystalline films from commercial silicon ingots. Large market applications are foreseen in the photovoltaic field, where important cost reductions are predicted, and also in advanced microelectronics technologies as three-dimensional integration, system on foil, or silicon interposers [Dross et al., Prog. Photovoltaics 20, 770-784 (2012); R.Brendel, Thin Film Crystalline Silicon Solar Cells (Wiley-VCH, Weinheim, Germany 2003); J. N. Burghartz, Ultra-Thin Chip Technology and Applications (Springer ScienceþBusiness Media, NY, USA, 2010)]. Existing methods produce “one at a time” silicon layers, once one thin film is obtained, the complete process is repeated to obtain the next layer. Here, we describe a technology that, from a single crystalline silicon wafer, produces a large number of crystalline films with controlled thickness in a single technological step.

  • Analysis of the dynamic short-circuit resistance in organic bulk-heterojunction solar cells: relation to the charge carrier collection efficiency

     Voz Sanchez, Cristobal; Puigdollers Gonzalez, Joaquin; Asensi López, José Miguel; Galindo Lorente, Sergi; Cheylan, S.; Pacios, R.; Ortega Villasclaras, Pablo Rafael; Alcubilla Gonzalez, Ramon
    Organic electronics
    Date of publication: 2013-06
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This work studies the charge carrier collection efficiency in organic bulk-heterojunction solar cells based on polymer:fullerene blends. An equivalent circuit with a specific recombination term is proposed to describe the behavior of this type of devices. It is experimentally shown that this recombination term determines the slope of the current-voltage characteristic at the short-circuit condition. The variation of this dynamic resistance with the light intensity can be interpreted considering a dominant first-order recombination process. Finally, an analytical model under a constant electric field approximation is presented that can be used to calculate the charge carrier collection efficiency of the device. This model can be also used to estimate an effective mobility-lifetime product, which is characteristic of the quality of the active layer.

    This work studies the charge carrier collection efficiency in organic bulk-heterojunction solar cells based on polymer:fullerene blends. An equivalent circuit with a specific recombination term is proposed to describe the behavior of this type of devices. It is experimentally shown that this recombination term determines the slope of the current–voltage characteristic at the short-circuit condition. The variation of this dynamic resistance with the light intensity can be interpreted considering a dominant first-order recombination process. Finally, an analytical model under a constant electric field approximation is presented that can be used to calculate the charge carrier collection efficiency of the device. This model can be also used to estimate an effective mobility–lifetime product, which is characteristic of the quality of the active layer.

  • Laser processing of Al2O3/a-SiCx:H stacks: a feasible solution for the rear surface of high-efficiency p-type c-Si solar cells

     Martin Garcia, Isidro; Ortega Villasclaras, Pablo Rafael; Colina Brito, Monica Alejandra; Orpella Garcia, Alberto; López, Gema; Alcubilla Gonzalez, Ramon
    Progress in photovoltaics
    Date of publication: 2013-08
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    We explore the potential of laser processing aluminium oxide (Al 2O3)/amorphous silicon carbide (a-SiCx:H) stacks to be used at the rear surface of p-type crystalline silicon (c-Si) solar cells. For this stack, excellent quality surface passivation is measured with effective surface recombination velocities as low as 2 cm/s. By means of an infrared laser, the dielectric film is locally opened. Simultaneously, part of the aluminium in the Al2O3 film is introduced into the c-Si, creating p+ regions that allow ohmic contacts with low-surface recombination velocities. At optimum pitch, high-efficiency solar cells are achievable for substrates of 0.5-2.5 O cm. Copyright © 2012 John Wiley & Sons, Ltd. We explore the potential of laser processing aluminium oxide (Al2O3)/amorphous silicon carbide (a-SiC x:H) stacks to be used at the rear surface of p-type crystalline silicon (c-Si) solar cells. For this stack, excellent quality surface passivation is measured with effective surface recombination velocities as low as 2 cm/s. By means of an infrared laser, part of the aluminium in the Al 2O3 film is introduced into the c-Si, creating p+ regions that allow ohmic contacts with low-surface recombination velocities.

    We explore the potential of laser processing aluminium oxide (Al2O3)/amorphous silicon carbide (a-SiCx:H) stacks to be used at the rear surface of p-type crystalline silicon (c-Si) solar cells. For this stack, excellent quality surface passivation is measured with effective surface recombination velocities as low as 2 cm/s. By means of an infrared laser, the dielectric film is locally opened. Simultaneously, part of the aluminium in the Al2O3 film is introduced into the c-Si, creating p+ regions that allow ohmic contacts with low-surface recombination velocities. At optimum pitch, high-efficiency solar cells are achievable for substrates of 0.5–2.5 Ω cm.

  • Boron diffused emitters passivated with Al2O3 films

     Masmitja Rusinyol, Gerard; Ortega Villasclaras, Pablo Rafael; Lopez Rodriguez, Gema; Calle Martin, Eric; Garcia Molina, Francisco Miguel; Martin Garcia, Isidro; Orpella Garcia, Alberto; Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon
    Spanish Conference on Electron Devices
    Presentation's date: 2013
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this work we study the fabrication and characterization of boron diffused emitters using FZ c-Si(n) substrates. Emitter surface was passivated with Al2O3(25 nm thick) layers deposited by thermal atomic layer deposition ALD technique. This study covers a broad emitter sheet resistance Rsh range from 20 to 250 O/sq using both polished and textured wafers. Emitter electrical quality was tested by means of lifetime measurements using quasi-stationary photoconductance QSS-PC method. Dark saturation emitter current densities Joe's were extracted from lifetime measurements resulting in Joe's values ranging from 10 to 150 fA/cm2 depending on Rsh. These results are in the-state-of-the-art in boron emitter passivation.

    In this work we study the fabrication and characterization of boron diffused emitters using FZ c-Si(n) substrates. Emitter surface was passivated with Al2O3(25 nm thick) layers deposited by thermal atomic layer deposition ALD technique. This study covers a broad emitter sheet resistance Rsh range from 20 to 250 Ω/sq using both polished and textured wafers. Emitter electrical quality was tested by means of lifetime measurements using quasi-stationary photoconductance QSS-PC method. Dark saturation emitter current densities Joe's were extracted from lifetime measurements resulting in Joe's values ranging from 10 to 150 fA/cm2 depending on Rsh. These results are in the-state-of-the-art in boron emitter passivation.

  • Progress in silicon heterojunction solar cell fabrication with rear laser-fired contacts

     Morales Vilches, Ana Belen; Voz Sanchez, Cristobal; Colina Brito, Monica Alejandra; Lopez Rodriguez, Gema; Martin Garcia, Isidro; Orpella Garcia, Alberto; Puigdollers Gonzalez, Joaquin; Garcia Rodriguez, Miguel; Alcubilla Gonzalez, Ramon
    Spanish Conference on Electron Devices
    Presentation's date: 2013-02
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Silicon Heterojunction (SHJ) solar cells are one of the most promising alternatives for high efficiency industrially feasible solar cells. The structure of these devices is based on hydrogenated amorphous silicon (a-Si:H) layers deposited at low temperature on crystalline silicon (c-Si) substrates. This fabrication process reduces the thermal stress on the substrate and is compatible with thinner wafers. In this work, we present our recent progress in the fabrication of SHJ solar cells on p-type c-Si wafers. The deposition conditions of hydrogenated amorphous silicon-carbon (a-SiCx:H) layers obtained by Plasma Enhanced Chemical Vapor Deposition (PECVD) are optimized. We have also applied a novel laser-firing process to contact the rear side of the fabricated devices. In this way, solar cells with point contacts through rear passivating layers can be fabricated without any photolithographic step.

  • An IBC solar cell for the UPC CubeSat-1 mission

     Ortega Villasclaras, Pablo Rafael; Jove Casulleras, Roger; Pedret, A; Gonzalvez, G.; Lopez Rodriguez, Gema; Martin Garcia, Isidro; Dominguez Pumar, Manuel M.; Alcubilla Gonzalez, Ramon; Camps Carmona, Adriano Jose
    Spanish Conference on Electron Devices
    Presentation's date: 2013-02
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this work the fabrication and electrical characterization of interdigitated back contact IBC solar cells is shown. These solar cells have been specifically designed for a CubeSat based satellite under developement at the Universitat Politecnica de Catalunya (UPC). Solar cells incorporate a transparent cover-glass as an extraterrestrial radiation shield. Front surface passivation was achieved using an Al2O3 layer exhibiting surface recombination velocities 100 cmls at the final device. Measurements confirm photovoltaic efficiencies n's-12%, with open circuit voltages Voc's 650 m V and short circuit current densities Jsc's 25 mA/cm 2. A module with 11 IBC solar cells interconnected in series will be integrated in one of the faces of the satellite forming part of the power subsystem. Preliminary results confirm the good electrical performance of the module.

    In this work the fabrication and electrical characterization of interdigitated back contact IBC solar cells is shown. These solar cells have been specifically designed for a CubeSat based satellite under developement at the Universitat Politecnica de Catalunya (UPC). Solar cells incorporate a transparent cover-glass as an extraterrestrial radiation shield. Front surface passivation was achieved using an Al2O3 layer exhibiting surface recombination velocities <; 100 cmls at the final device. Measurements confirm photovoltaic efficiencies η's-12%, with open circuit voltages Voc's ~650 m V and short circuit current densities Jsc's ~25 mA/cm2. A module with 11 IBC solar cells interconnected in series will be integrated in one of the faces of the satellite forming part of the power subsystem. Preliminary results confirm the good electrical performance of the module.

  • Impact of metallization techniques of surface passivation of high efficiency crystalline silicon solar cells

     Coll Valenti, Arnau; Martin Garcia, Isidro; Ortega Villasclaras, Pablo Rafael; Bermejo Broto, Alexandra; López, Gema; Alcubilla Gonzalez, Ramon
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2013-10-02
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Most of the high-efficiency c-Si solar cells are based on dielectric films that electrically passivate c-Si surface and must keep their passivation properties after metal deposition on top of them. This work studies the impact of three different aluminum Physical Vapor Deposition (PVD) methods (thermal, e-beam, sputtering) on the c-Si surface passivation provided by SiO2 and Al2O3 films. Effective surface recombination velocity is measured before and after metal deposition. Results show that e-beam and sputtering techniques degrade surface passivation while thermal evaporation has no impact. Surface passivation can be recovered and even improved by means of an annealing with the aluminum film on top of the dielectric leading to the so-called alnealing. Additionally, after this alnealing Capacitance-Voltage measurements and lifetime spectroscopy analysis suggest a strong dependence of fixed charge density for SiO2 films on the metal deposition technique that helps in c-Si surface passivation.

  • Single-Step multiple-layers wafer slicing from macroporous silicon

     Garin Escriva, Moises; Hernández García, David; Todorov Trifonov, Trifon; Cardador, D.; Alcubilla Gonzalez, Ramon
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2013-10-01
    Presentation of work at congresses

    Read the abstract Read the abstract  Share Reference managers Reference managers Open in new window

    There is a rising interest, from both photovoltaics and microelectronics industry, in wafer thickness reduction. During the last decade, it has been steadily reduced from 350 µm to 180 µm, but benefits are foreseen for thicknesses well below these values. The current sawing technology, however, suffers from large kerf losses and further reductions are increasingly difficult. Several technologies have emerged aiming to produce thin Si foils from a wafer, such as layer transfer, induced cleaving, or pore reorganization. These methods produce a single layer by step. In this work we report on a method able to produce many crystalline layers from a single silicon wafer and in a single fabrication step.

  • DopLaCell: a new c-Si solar cell based on laser processing of dielectric films

     Martin Garcia, Isidro; Lopez Gonzalez, Juan Miguel; Colina Brito, Monica Alejandra; Orpella Garcia, Alberto; Alcubilla Gonzalez, Ramon
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2013-10-01
    Presentation of work at congresses

    Read the abstract Read the abstract  Share Reference managers Reference managers Open in new window

    In this paper we introduce a new crystalline silicon (c-Si) solar cell fabrication technology based on the laser processing of dielectric films to create all the highly-doped regions. We call it DopLaCell (Doped by Laser Cell) structure. The resulting fabrication process can be simplified to just four steps: wafer cleaning, film depositions, laser processing and metallization. We used phosphorus-doped silicon carbide stacks (SiCx(n)) and aluminium oxide/silicon carbide (Al2O3/SiCx) stacks for the creation of n+ and p+ regions respectively. As a proof of concept, 1x1 cm2 solar cells were fabricated on 0.45 Wcm p-type substrates with promising results. The main feature of DopLaCell structure is the location of the emitter at the rear surface consisting of a point-like laser processed n+ regions combined with an induced inversion layer in between based on the fixed charge density of the SiCx(n) stacks. Solar cells with distance between rear emitter regions or pitch ranging from 200 to 350 µm are characterized resulting in a strong decrease of Fill Factor (FF) from 75.4 to 59.7 %. Suns-Voc measurements show excellent pseudo-FF (p-FF) values beyond 81% in all devices demonstrating the high quality of laser doping process and the actual limitation of FF by ohmic losses. Device modelling through 3D simulations demonstrates that these ohmic losses are related to the high sheet resistance of the inversion layer induced in-between n+ regions. We conclude that there is room for improvement to fully develop the potential of this new structure, particularly for low resistivity n-type substrates where the high fixed charge densities of Al2O3 can help to improve FF.

  • Silicon heterjunction for advanced rear contact cells: main results of the SHARCC project

     Desrues, T.; Martin Garcia, Isidro; de Vecchi, S.; Abolmasov, S.; Diouf, D.; Lukyanov, A.; Ortega Villasclaras, Pablo Rafael; Colina Brito, Monica Alejandra; Versavel, M.; Tuseau, M.; Souche, F.; Nychyporuk, T.; Gueunier-Farret, M.; Muñoz, D.; Lemiti, M.; Kleider, J.P.; Cabarrocas, P. Roca; Alcubilla Gonzalez, Ramon; Schlumberger, Y.; Ribeyron, P.J.
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2013-09-30
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This paper presents the main results of a research project called SHARCC, focused on rear contacted silicon heterojunction solar cells. Within this project, funded by the French National Research Agency (ANR), different tasks were shared by the partners taking into account their specific skills. This project led to efficiencies about 19% on innovative cell structures obtained with an industrial process based on laser ablation. Keywords: silicon heterojunction, back contact

  • 3D simulations of back-contact back-junction c-Si(P) solar cells with doped point contacts

     Carrió, D.; Ortega Villasclaras, Pablo Rafael; López, Gema; Lopez Gonzalez, Juan Miguel; Martin Garcia, Isidro; Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2013-10-02
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    The back-contact back-junction BC-BJ solar cell concept is a promising photovoltaic structure for both laboratory and industrial c-Si solar cells. High efficiency devices based on this concept have been reported in the past using either diffused regions or applying the heterojunction with intrinsic thin layer HIT concept to perform both base and emitter contacts. In this work we use 3D numerical simulations to study the impact of technological parameters on device performance of c-Si(p) BC-BJ solar cells with point-like doped contacts. Numerical simulations allow us to optimize rear contact geometry as a trade-off between recombination and base resistive losses, leading to photovoltaic efficiencies higher than 18.3% and up to 22.3% on 2.2 ¿cm FZ substrates depending on the back contact pattern and the passivation quality of base contacts.

  • Células solares de heterounión de silicio: alta eficiencia en procesos de fabricación a baja temperatura

     Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon
    Revista española de física
    Date of publication: 2013-02
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Las células de heterounión de silicio se basan en uniones formadas entre sustratos de silicio cristalino y capas de silicio amorfo hidrogenado depositadas a baja temperatura. El proceso de fabricación de estos dispositivos reduce el estrés térmico sobre los sustratos, lo que resulta más adecuado para la utilización de obleas más delgadas. Por tanto, esta tecnología aparece como una interesante alternativa a las tradicionales uniones pn de silicio obtenidas en procesos de difusión a alta temperatura. Las células de heterounión de silicio ya han alcanzado altas eficiencias, tanto a escala de laboratorio como en procesos de producción industrial. Actualmente, esta tecnología se está combinando con nuevos procesos de fabricación asistidos por láser a la vez que se desarrollan nuevas estructuras de célula solar.

  • Access to the full text
    Surface passivation and optical characterization of Al2O3/a-SiCx stacks on c-Si substrates  Open access

     Lopez Rodriguez, Gema; Ortega Villasclaras, Pablo Rafael; Voz Sanchez, Cristobal; Martin Garcia, Isidro; Colina Brito, Monica Alejandra; Morales Vilches, Ana Belen; Orpella Garcia, Alberto; Alcubilla Gonzalez, Ramon
    Beilstein Journal of Nanotechnology
    Date of publication: 2013-11-06
    Journal article

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    The aim of this work is to study the surface passivation of aluminum oxide/amorphous silicon carbide (Al2O3/a-SiCx) stacks on both p-type and n-type crystalline silicon (c-Si) substrates as well as the optical characterization of these stacks. Al2O3 films of different thicknesses were deposited by thermal atomic layer deposition (ALD) at 200 °C and were complemented with a layer of a-SiCx deposited by plasma-enhanced chemical vapor deposition (PECVD) to form anti-reflection coating (ARC) stacks with a total thickness of 75 nm. A comparative study has been carried out on polished and randomly textured wafers. We have experimentally determined the optimum thickness of the stack for photovoltaic applications by minimizing the reflection losses over a wide wavelength range (300–1200 nm) without compromising the outstanding passivation properties of the Al2O3 films. The upper limit of the surface recombination velocity (Seff,max) was evaluated at a carrier injection level corresponding to 1-sun illumination, which led to values below 10 cm/s. Reflectance values below 2% were measured on textured samples over the wavelength range of 450–1000 nm.

  • Design, synthesis, characterization and development of novel organic conducting polymers with technological applications  Open access

     Aradilla Zapata, David
    Defense's date: 2013-01-11
    Department of Chemical Engineering, Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    In this thesis, a series of novel organic conducting polymers have been synthesized using alternative methods based on electrochemical techniques, which have allowed to broaden the knowledge in the field of the characterization by means of topological, spectroscopic, electrochemical and structural techniques. Among the variety of synthesis techniques of conducting polymers, layer-by-layer (LbL) has been one of the most important to build multilayered systems. Thus, in this thesis the LbL has shown to be an excellent procedure to explore new applications in the field of energy storage using conducting polymers. On the other hand, recently, the influence of new sustituents on functionalized conducting polymers has been proved to modify the structural, optical and physical properties of conducting polymers. Within this context, synthesis of novel functionalized conducting polymers bearing strong electron-withdrawing sustituents such as cyano group or halide atoms have been widely studied and characterized throughout this thesis. The presence of these substituents have emerged as promising candidates in the field of chemical sensors and electrochromic devices. Although the functionality of polymers or the development of new techniques are excellent procedures to synthesize and to develop new properties on the field of conducting polymers, it is worth mentioning that the substrate plays a crucial role on the electrochemical field. Accordingly, the substrates can also modify and change the properties of conducting polymers during the electropolymerization process. In this way, different substrates were employed in this work with the aim of achieving new applications in the field of corrosion inhibitors and as supercapacitors. Supercapacitors as energy storage device has been an outstanding application during this thesis. Thus, the field of nanotechnology has taken an important part in this thesis through development and design of promising hybrid nanocomposites based on conducting polymers and clay with technological applications and interesting optoelectronic properties. The contribution of theoretical techniques based on quantum mechanical calculations have allowed to predict some electronic and structural properties of conjugated polymers, which could be corroborated experimentally. The quantum mechanics is a useful tool to check experimental results and to understand mechanisms not fully understood at experimental level. Therefore, theoretical calculations have provided promising information to obtain new insights in the field of conducting polymers.

    La presente tesis se encuentra focalizada en el estudio de nuevos polímeros conductores orgánicos obtenidos a partir de métodos alternativos basados en principios electroquímicos. Entre los principales métodos de polimerización la técnica conocida como capa-a-capa ha emergido con gran fuerza en los últimos años dada sus numerosas ventajas y propiedades. En este contexto, la síntesis de polímeros conductores mediante este procedimiento permitió comprender y analizar el efecto sinérgico entre capas, consiguientemente la caracterización de estos nuevos materiales a partir de técnicas estructurales, espectroscópicas, morfológicas, electroquímicas y ópticas permitió indagar y desarrollar aplicaciones en diferentes campos tecnológicos tales como la electrónica o la corrosión. Otro de los factores que influyen en las propiedades de los polímeros conductores es el proceso de funcionalización. En esta tesis, la incorporación de grupos funcionales con elevado carácter aceptor de electrones centró una parte importante del trabajo, de este modo, los polímeros conductores funcionalizados con átomos halogenados o mediante el grupo ciano evidenciaron una gran influencia en las propiedades físicas, estructurales, ópticas y morfológicas de las estructuras químicas en tiofeno y pirrol. La modificación de determinadas propiedades en estos polímeros permitió desarrollar componentes basados en sensores químicos o dispositivos electrocrómicos. Acorde a esta temática, la modificación de la superficie juega también un papel importante y crucial en las propiedades de los polímeros conductores durante el proceso de síntesis electroquímica. Análogamente al caso de la funcionalización el estudio de la modificación de la superficie denotó una gran expectativa en el desarrollo de nuevos supercondensadores orgánicos, así como una gran alternativa para aplicación como inhibidores de corrosión. Finalmente, en el ámbito experimental de esta tesis, se han orientado estudios en el campo de la nanotecnología en la síntesis y caracterización de nuevos materiales híbridos nanocompuestos con interesantes propiedades optoelectrónicas y electroquímicas. A nivel teórico, la contribución de cálculos teóricos basados en mecánica quántica permitieron predecir determinadas propiedades electrónicas y estructurales de polímeros conductores, cuyos valores fueron corroborados experimentalmente. Así, la química teórica proporcionó un amplio conocimiento en la exploración y comprensión de los mecanismos estructurales de los polímeros conductores.

  • Advanced AlGaN/GaN HEMT technology, design, fabrication and characterization  Open access

     Fontserè Recuenco, Abel
    Defense's date: 2013-07-23
    Department of Electronic Engineering, Universitat Politècnica de Catalunya
    Theses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Nowadays, the microelectronics technology is based on the mature and very well established silicon (Si) technology. However, Si exhibits some important limitations regarding its voltage blocking capability, operation temperature and switching frequency. In this sense, Gallium Nitride (GaN)-based high electron mobility transistors (HEMTs) devices have the potential to make this change possible. The unique combination of the high-breakdown field, the high-channel electron mobility of the two dimensional electron gas (2DEG), and high-temperature of operation has attracted enormous interest from social, academia and industry and in this context this PhD dissertation has been made. This thesis has focused on improving the device performance through the advanced design, fabrication and characterization of AlGaN/GaN HEMTs, primarily grown on Si templates. The first milestone of this PhD dissertation has been the establishment of a know-how on GaN HEMT technology from several points of view: the device design, the device modeling, the process fabrication and the advanced characterization primarily using devices fabricated at Centre de Recherche sur l'Hétéro-Epitaxie (CRHEA-CNRS) (France) in the framework of a collaborative project. In this project, the main workhorse of this dissertation was the explorative analysis performed on the AlGaN/GaN HEMTs by innovative electrical and physical characterization methods. A relevant objective of this thesis was also to merge the nanotechnology approach with the conventional characterization techniques at the device scale to understand the device performance. A number of physical characterization techniques have been imaginatively used during this PhD determine the main physical parameters of our devices such as the morphology, the composition, the threading dislocations density, the nanoscale conductive pattern and others. The conductive atomic force microscopy (CAFM) tool have been widely described and used to understand the conduction mechanisms through the AlGaN/GaN Ohmic contact by performing simultaneously topography and electrical conductivity measurements. As it occurs with the most of the electronic switches, the gate stack is maybe the critical part of the device in terms of performance and longtime reliability. For this reason, how the AlGaN/GaN HEMT gate contact affects the overall HEMT behaviour by means of advanced characterization and modeling has been intensively investigated. It is worth mentioning that the high-temperature characterization is also a cornerstone of this PhD. It has been reported the elevated temperature impact on the forward and the reverse leakage currents for analogous Schottky gate HEMTs grown on different substrates: Si, sapphire and free-standing GaN (FS-GaN). The HEMT' forward-current temperature coefficients (T^a) as well as the thermal activation energies have been determined in the range of 25-300 ºC. Besides, the impact of the elevated temperature on the Ohmic and gate contacts has also been investigated. The main results of the gold-free AlGaN/GaN HEMTs high-voltage devices fabricated with a 4 inch Si CMOS compatible technology at the clean room of the CNM in the framework of the industrial contract with ON semiconductor were presented. We have shown that the fabricated devices are in the state-of-the-art (gold-free Ohmic and Schottky contacts) taking into account their power device figure-of-merit ((VB^2)/Ron) of 4.05×10^8 W/cm^2. Basically, two different families of AlGaN/GaN-on-Si MIS-HEMTs devices were fabricated on commercial 4 inch wafers: (i) using a thin ALD HfO2 (deposited on the CNM clean room) and (ii) thin in-situ grown Si3N4, as a gate insulator (grown by the vendor). The scientific impact of this PhD in terms of science indicators is of 17 journal papers (8 as first author) and 10 contributions at international conferences.

  • Optimization of laser doping processes for the creation of p+ regions from solid dopant sources

     Colina Brito, Monica Alejandra; Martin Garcia, Isidro; Voz Sanchez, Cristobal; Morales Vilches, Ana Belen; Ortega Villasclaras, Pablo Rafael; Lopez Rodriguez, Gema; Orpella Garcia, Alberto; Alcubilla Gonzalez, Ramon; Sánchez Aniorte, M. Isabel; Molpeceres Alvarez, Carlos
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2012-09
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Laser processing for high efficiency c-Si solar cells

     Alcubilla Gonzalez, Ramon
    Workshop Nanophotonics for Photovoltaics, a step forward
    Presentation's date: 2012-11-06
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Optimization of al2o3 films obtained by ald to passivate p-type c-silicon wafers

     Lopez Rodriguez, Gema; Ortega Villasclaras, Pablo Rafael; Martin Garcia, Isidro; Colina Brito, Monica Alejandra; Orpella Garcia, Alberto; Alcubilla Gonzalez, Ramon
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2012-09
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Low recombination n+ regions created by n+ c-Si epitaxial layers and laser processing of phosphorus-doped SiCx films

     Martin Garcia, Isidro; Colina Brito, Monica Alejandra; Orpella Garcia, Alberto; Voz Sanchez, Cristobal; De Vecchi, S.; Desrues, T.; Abolmasov, S.; Roca i Cabarrocas, P.; Alcubilla Gonzalez, Ramon
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2012-09
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Influence of laser wavelength on laser-fired contacts for crystalline silicon solar cells

     Sanchez Aniorte, Maria Isabel; Muñoz Martín, D.; Morales Furio, Miguel; Ortega Villasclaras, Pablo Rafael; Martin Garcia, Isidro; Colina Brito, Monica Alejandra; Alcubilla Gonzalez, Ramon; Molpeceres Alvarez, Carlos
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2012-09
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Influence of wavelength on laser doping and laser-fired contact processes for c-Si solar cells

     Molpeceres Alvarez, Carlos; Sanchez Aniorte, Maria Isabel; Morales Furio, Miguel; Muñoz, David; Martin Garcia, Isidro; Ortega Villasclaras, Pablo Rafael; Colina Brito, Monica Alejandra; Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon
    SPIE Optics+Photonics
    Presentation's date: 2012-08-15
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This work investigates the influence of the laser wavelength on laser doping (LD) and laser - fired contact (LFC) formation in solar cell structures . We compare the results obtained using the three first harmonics (corresponding to wavelengths of 1064 nm, 532 nm and 355 nm) of fully commercial solid state laser sources with pulse width in the ns range. The discussion is based on the impact on the morphology and electrical characteristics of test structures. In the case of LFC the study includes th e influence of different passivation layers and the assessment of the process quality through electrical resistance measurements of an alumin i um single LFC point for the different wavelengths. Values for the normalized LFC resistance far below 1 .0 m Ω cm 2 have been obtained, with better results at s horter wavelen g ths. To assess the influence of the laser wavelength on LD we have created n+ regions into p - type c - Si wafers , using a dry LD approach to define punctual emitters. J - V characteristics show exponen tial trends at mid - injection for a broad parametric window in all wavelengths, with local ideality factors well below 1.5. In bot h processes the best results have been obtained using green (532 nm) and , specially, UV (355 nm) . This indicates that to minim ize the thermal damage in the material is a clear requisite to obtain th e best electrical performance, thus indicating that UV laser shows better potential to be used in high efficiency solar cells.

  • Laser-fired contact optimization in c-Si solar cells

     Ortega Villasclaras, Pablo Rafael; Orpella Garcia, Alberto; Martin Garcia, Isidro; Colina Brito, Monica Alejandra; Lopez Rodriguez, Gema; Voz Sanchez, Cristobal; Sánchez, Isabel; Molpeceres Alvarez, Carlos; Alcubilla Gonzalez, Ramon
    Progress in photovoltaics
    Date of publication: 2012-03
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this work we study the optimization of laser-fired contact (LFC) processing parameters, namely laser power and number of pulses, based on the electrical resistance measurement of an aluminum single LFC point. LFC process has been made through four passivation layers that are typically used in c-Si and mc-Si solar cell fabrication: thermally grown silicon oxide (SiO2), deposited phosphorus-doped amorphous silicon carbide (a-SiCx/H(n)), aluminum oxide (Al2O3) and silicon nitride (SiNx/H) films. Values for the LFC resistance normalized by the laser spot area in the range of 0.65–3 mΩ cm2 have been obtained.

  • Comparison between the density-of-states of picene transistors measured in air and under vacuum

     Voz Sanchez, Cristobal; Marsal Vinade, Albert; Moreno Sierra, Cesar; Puigdollers Gonzalez, Joaquin; Alcubilla Gonzalez, Ramon
    Synthetic metals
    Date of publication: 2012-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Picene has recently attracted much attention as the active layer in organic thin-film transistors because of its good performance in air. In this work, we have fabricated picene thin-film transistors that exhibit field-effect mobilities up to 1.3 cm2 V−1 s−1 and on/off ratios above 105 in ambient conditions. These devices have been electrically characterized over the temperature range 300–360 K in air and also under vacuum conditions. In particular, the thermal activation energy of the channel conductance as a function of the gate bias has been measured. The dependence of the activation energy on the gate bias corresponds to a gradual shift of the Fermi level towards the HOMO level as more gap states are filled by trapped holes. The density-of-states can be estimated from the derivative of the activation energy with respect to gate bias. The calculated density-of-states is compared for devices measured in air and under vacuum conditions. These results can help to understand the gas sensing capability of picene, together with its enhanced electrical performance after air exposure.

  • Organic metal¿organic semiconductor blended contacts in single crystal field-effect transistors

     Pfattner, Raphael; Mas Torrent, Marta; Moreno, Cesar; Puigdollers Gonzalez, Joaquin; Alcubilla Gonzalez, Ramon; Bilotti, I.; Venuti, E.; Brillante, Aldo; Laukhin, V.; Veciana, Jaume; Rovira, Concepció
    Journal of materials chemistry
    Date of publication: 2012-06-25
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Access to the full text
    Emissive properties of SiO2 thin films through photonic windows  Open access

     Hernández García, David; Garin Escriva, Moises; Todorov Trifonov, Trifon; Rodriguez Martinez, Angel; Alcubilla Gonzalez, Ramon
    Applied physics letters
    Date of publication: 2012-02
    Journal article

    Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

  • CMOS processing for MEMS devices and their applications

     Montanyà Silvestre, Josep
    Defense's date: 2012-01-18
    Department of Electronic Engineering, Universitat Politècnica de Catalunya
    Theses

     Share Reference managers Reference managers Open in new window

  • 27th EU PVSEC Poster Award

     Colina Brito, Monica Alejandra; Voz Sanchez, Cristobal; Martin Garcia, Isidro; Alcubilla Gonzalez, Ramon; Ortega Villasclaras, Pablo Rafael; Lopez Rodriguez, Gema; Morales Vilches, Ana Belen; Sánchez Aniorte, M. Isabel; Molpeceres Alvarez, Carlos
    Award or recognition

    View View Open in new window  Share

  • Dopado con láser del silicio cristalino: aplicación a emisores selectivos y nuevas estructuras de células solares

     Orpella Garcia, Alberto; Alcubilla Gonzalez, Ramon; Martin Garcia, Isidro
    Participation in a competitive project

     Share

  • P-type c-Si solar cells based on rear side laser processing of Al 2O 3/SiC x stacks

     Ortega Villasclaras, Pablo Rafael; Martin Garcia, Isidro; Lopez Rodriguez, Gema; Colina Brito, Monica Alejandra; Orpella Garcia, Alberto; Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon
    Solar energy materials and solar cells
    Date of publication: 2012-11
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Método para el dopado selectivo de un semiconductor mediante transferencia inducida por láser

     Colina Brito, Monica Alejandra; Voz Sanchez, Cristobal; Martin Garcia, Isidro; Alcubilla Gonzalez, Ramon; Molpeceres Alvarez, Carlos; Sanchez Aniorte, Maria Isabel
    Date of request: 2012-07-06
    Invention patent

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Método para el dopado selectivo de un semiconductor mediante transferencia inducida por láser, que comprende un sistema precursor (200) compuesto de al menos una capa absorbente (202) a la radiación láser, con una solución dopante (203) y un soporte transparente (201) , el cual se coloca enfrentado y en contacto directo con el sistema receptor (300) donde se integra el substrato (301) semiconductor y se irradia con uno o más pulsos de un haz láser (100) focalizados en la interfaz entre la fuente y el substrato, provocando la transferencia de material proveniente de la fuente hacia el substrato y la introducción de átomos dopantes provenientes de la fuente dentro del substrato semiconductor. El sustrato (301) es, preferentemente, una oblea de silicio con una cara frontal (302) y una cara posterior (303) con capas pasivante antirreflejo dieléctricas.

  • Procedimiento para la obtención de múltiples capas de silicio cristalino a partir de una oblea de silicio

     Alcubilla Gonzalez, Ramon; Todorov Trifonov, Trifon; Hernández García, David; Garin Escriva, Moises
    Date of request: 2012-06-13
    Invention patent

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    Procedimiento para la obtención de múltiples capas de silicio cristalino a partir de una oblea de silicio.

    Se divulga un método y sistema para la fabricación de multicapas de silicio cristalino a partir de una oblea de silicio por el cual se puede controlar el grosor de las distintas capas para que varíe desde la escala de cientos de nanómetros a la escala de decenas de micrómetros. El método de fabricación comprende etapas de litografía, de ataques electroquímicos, y recristalización de la oblea al mismo tiempo que se controlan los parámetros de reacción.

  • Access to the full text
    Crystalline silicon solar cells beyond 20% efficiency  Open access

     Ortega Villasclaras, Pablo Rafael; Lopez Rodriguez, Gema; Orpella Garcia, Alberto; Colina Brito, Monica Alejandra; Martin Garcia, Isidro; Voz Sanchez, Cristobal; Bermejo Broto, Alexandra; Puigdollers Gonzalez, Joaquin; Garcia Molina, Miguel; Alcubilla Gonzalez, Ramon
    Spanish Conference on Electron Devices
    Presentation's date: 2011-02-08
    Presentation of work at congresses

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    —This paper describes a fabrication process to obtain high efficiency c-Si cells (> 20%) based on the Laser Fired Contact Passivated Emitter Rear Cell (LFC-PERC) concept. Photovoltaic efficiencies beyond 20% have been achieved using thermal SiO2 as a rear passivation layer on 2 cm x 2 cm solar cells with 0.45 cm Fz c-Si substrates. Efficiencies up to 22% are expected for material resistivities in the 0.4–5 cm using an optimized rear contact grid

  • Low voltage operating complementary inverters fabricated at low temperature

     Puigdollers Gonzalez, Joaquin; Marsal Vinade, Albert; Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon
    Spanish Conference on Electron Devices
    Presentation's date: 2011-02-09
    Presentation of work at congresses

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Electronic and structural characterisation of a tetrathiafulvalene compound as a potential candidate for ambipolar transport properties

     Oton, Francisco; Pfattner, Raphael; Pavlica, Egon; Olivier, Yoann; Bratina, Gvido; Cornil, Jerome; Puigdollers Gonzalez, Joaquin; Alcubilla Gonzalez, Ramon; Fontrodona, Xavier; Mas Torrent, Marta; Veciana, Jaume; Rovira, Concepcio
    Crystengcomm
    Date of publication: 2011
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • SiC oxidation processing technology for MOSFET devices fabrication

     Constant, Aurore
    Defense's date: 2011-07-25
    Department of Electronic Engineering, Universitat Politècnica de Catalunya
    Theses

     Share Reference managers Reference managers Open in new window

  • Q-00026

     Alcubilla Gonzalez, Ramon
    Participation in a competitive project

     Share

  • Evidence of intrinsic ambipolar charge transport in a high band gap organic semiconductor

     Moreno Sierra, Cesar; Pfattner, Raphael; Mas Torrent, Marta; Puigdollers Gonzalez, Joaquin; Bromley, Stephan; Rovira, Concepció; Alcubilla Gonzalez, Ramon; Veciana, Jaume
    Journal of materials chemistry B
    Date of publication: 2011-11-16
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Theoretical and experimental investigations combining in situ Kelvin probe microscopy (KPM) and macroscopic electrical studies are employed to explore the intrinsic transport in dithiophene-tetrathiafulvalene (DT-TTF) single crystal organic field-effect transistors. Our work demonstrates that ambipolar behavior is not restricted only to materials possessing a high electron affinity and thus may be a more general phenomenon.

  • Laser fired contacts applied to the rear surface of heterojunction silicon solar cells

     Martin Garcia, Isidro; Labrune, M.; Salomon, A.; Roca i Cabarrocas, P.; Alcubilla Gonzalez, Ramon
    Solar energy materials and solar cells
    Date of publication: 2011-11
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    In this work, we fabricate heterojunction silicon solar cells on p-type substrates whose rear surface configuration is based on dielectric passivation and laser fired contacts (LFC cells). This is an alternative to boron-doped amorphous silicon film, with which we also fabricate solar cells for direct comparison (HJ cells). As substrates, 3.5 and 0.8 Ω cm p-type double-side polished FZ c-Si wafers are used. Regarding surface passivation for highly doped substrates, LFC configuration has some advantage due to the higher difficulty in creating an efficient amorphous back surface field. Additionally, those substrates are also more advantageous in terms of carrier injection when the rear surface is locally contacted. Thus LFC cells made on 0.8 Ω cm substrates reach Voc values up to 680 mV, in the same range as that of their HJ cell counterpart, with better FF demonstrating that LFC configuration is a feasible alternative for highly doped substrates. Focusing on the impact of the distance between rear contacts on cell performance, we found a trade-off between open circuit voltage Voc and fill factor FF. Finally electroluminescence characterization and the dependence of Voc on pitch, modeled by Fischer's equation, indicate that the depassivated area due to the laser processing of the contacts is bigger than the contacted area.

  • Células fotovoltaicas con un rendimiento del 20.5%

     Ortega Villasclaras, Pablo Rafael; Lopez Rodriguez, Gema; Orpella Garcia, Alberto; Martin Garcia, Isidro; Colina Brito, Monica Alejandra; Voz Sanchez, Cristobal; Bermejo Broto, Alexandra; Puigdollers Gonzalez, Joaquin; Garcia Molina, Francisco Miguel; Alcubilla Gonzalez, Ramon
    Solar News
    Date of publication: 2011-03-01
    Journal article

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Un grupo de investigadores de la Universitat Politècnica de Catalunya (UPC) han desarrollado un proceso de fabricación que permite obtener rendimientos de conversión fotovoltaicos del 20,5%. Esto supone una mejora sustancial con respecto a los rendimientos habituales en células comerciales que sitúa en un 15%, y la cuota más elevada a la que se ha llegado hasta ahora en España. En estos momentos trabajan en mejoras que las hagan accesibles industrialmente. El avance, tras años de investigación, consiste en minimizar los diferentes mecanismos de pérdidas que influyen en el cómputo de la eficiencia de conversión fotovoltaica.

  • Simultaneous gettering and emitter formation in multicrystalline-Si wafers by annealing phosphorus doped amorphous silicon compounds

     Ferré, R.; Martin Garcia, Isidro; Trassl, Roland; Alcubilla Gonzalez, Ramon; Brendel, Rolf
    Applied physics letters
    Date of publication: 2011-01-10
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Density-of-states in pentacene from the electrical characteristics of thin-film transistors

     Puigdollers Gonzalez, Joaquin; Marsal Vinade, Albert; Cheylan, S.; Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon
    Organic electronics
    Date of publication: 2010-08
    Journal article

    View View Open in new window  Share Reference managers Reference managers Open in new window

  • Optimization of the ohmic contact to AlGaN/GaN HEMTs

     Fontserè, Abel; Alcubilla Gonzalez, Ramon; Pérez Tomás, Amador
    Barcelona Forum on Ph.D. Research in Communications, Electronics and Signal Processing
    Presentation's date: 2010-10-21
    Presentation of work at congresses

     Share Reference managers Reference managers Open in new window

  • Macroporous silicon : a next generation catalytic monolith for ethanol steam reforming

     Vega, Didac; Todorov Trifonov, Trifon; Hernández García, David; Rodriguez Martinez, Angel; Alcubilla Gonzalez, Ramon; Jiménez, Nuria; Llorca Pique, Jordi; López, E.
    International conference on Porous Semiconductors Science and Technology
    Presentation's date: 2010-03
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    Macroporous silicon membranes, consisting of straight parallel pores with a diameter of 3.3μm and depth/width ratio >60, are used as microreactors for high efficiency hydrogen generation via steam reforming of ethanol. The inner walls of the pores were coated with Co3O3*ZnO catalyst film. The as-prepared reactors were fed with water-ethanol gas mixture and the effect of the reactor temperature and inlet flow rate on the H2 generation was studied. We observed a superior H2 generation efficiency in comparison with conventional microreactors.

  • Optimization of the rear point contact scheme of crystalline silicon solar cells using laser-fired contacts

     Ortega Villasclaras, Pablo Rafael; Orpella Garcia, Alberto; López, Gema; Martin Garcia, Isidro; Voz Sanchez, Cristobal; Alcubilla Gonzalez, Ramon; Colina Brito, Monica Alejandra; Sánchez Aniorte, M. Isabel; Perales, Francisco; Molpeceres Alvarez, Carlos
    European Photovoltaic Solar Energy Conference and Exhibition
    Presentation's date: 2010-09-06
    Presentation of work at congresses

    Read the abstract Read the abstract View View Open in new window  Share Reference managers Reference managers Open in new window

    This paper is focused on the optimization of the rear contact scheme of p-type c-Si LFC-PERC high efficiency solar cells minimizing base ohmic losses without jeopardize rear passivation. This is carried out optimizing on one hand the LFC laser conditions for minimum point resistance and on the other hand through a proper design of the contact grid layout finding the optimum trade off for a given base resistivity between rear passivation and base resistance. LFC process was carried out through 110 nm thermal SiO2 passivation layer using IR and green lasers. Very low specific contact resistances, 0.1 mcm2 have been achieved independently of the laser used. For optimum rear contacted area fraction efficiencies over 21.5% and 22%, for IR and green lasers respectively are expected in the 0.5-5 cm resistivity range.

  • Access to the full text
    Interchain and intrachain emission branching in polymer light-emitting diode doped by organic molecules  Open access

     Krautz, D.; Lunedei, E.; Puigdollers Gonzalez, Joaquin; Badenes, Gonçal; Alcubilla Gonzalez, Ramon; Cheylan, S.
    Applied physics letters
    Date of publication: 2010-01-18
    Journal article

    Read the abstract Read the abstract Access to the full text Access to the full text Open in new window  Share Reference managers Reference managers Open in new window

    A blend of the polymer poly 2- 2-ethylhexyloxy -5-methoxy-1,4-phenylenevinylene MEH-PPV and the electron-transport molecule tris- 8-hydroxyquinoline aluminum Alq3 has been investigated by means of electroluminescence and fluorescence spectroscopy, upon variation of the Alq3 content in the blend.Adecreased interchain emission is observed upon increasing Alq3 content, due to lower packing of the MEH-PPV chains which leads to a reduction in the interchain interaction, excimer formation, and emission probability. A branching of MEH-PPV interchain and intrachain emissive contributions is clearly time resolved and analyzed as a function of the Alq3 content. At high doping concentration, direct emission from Alq3 molecules is observed.