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35th European Photovoltaic Solar Energy Conference and Exhibition; 653-656, In the last years, our research group has focused on the development of Interdigitated Back Contacted (IBC) solar cells based on transition metal oxides. In particular, a very thin Al2O3/TiO2 stack deposited by ALD has demonstrated excellent results. The point of this work is to try to develop a transparent conductive oxide that could be inserted in between the passivating layers and the metal contact in order to improve rear reflector properties. As a good candidate, we focus on Zinc Oxide (ZnO) deposited from DEZ (Ditehylzinc) and water as gas precursors. A deposition rate of 1.76 A/cycle is found for layers deposited at 125 ºC indicating a self-limited reaction, i.e. atomic layer deposition process. This film has an optical band gap of 3.26 eV demonstrating good optical properties to work as a back reflector. Unfortunately, contact quality with these layers is very poor. In order to investigate the origin of such a poor performance, we measure ZnO workfunction by Scanning Kelvin Probe resulting in 4.85 eV. This value suggests that the developed ZnO films could work better in a hole selective contact. To demonstrate this point, contacts on MoOx layers were fabricated leading to reasonable contact resistance values of 43 mcm. Passivation properties of these contacts will be addressed in the future in order to consider their introduction into the final IBC solar cell.

33rd European Photovoltaic Solar Energy Conference and Exhibition; 857-860, Black silicon (b-Si) reduces drastically light reflectance in the front side of c-Si solar cells to values near zero for the whole absorbed solar spectrum. In this work, we apply 2D and 3D simulations to explore the efficiency limits of interdigitated back-contacted c-Si(n) solar cells with line or point contacts respectively, using ALD Al2O3 passivated b-Si in the front surface. Realistic physical and technological parameters involved in a conventional oven-based fabrication process are considered in the simulations, especially those related to surface recombination on the b-Si as well as high doped p+/n+ strip regions. One important issue is the temporal stability of surface passivation on b-Si surfaces. In this work experimental long-term b-Si surface passivation data after two years and its impact on cell performance are studied. Simulations demonstrate initial and final photovoltaic efficiencies over 24.6% and 23.2% respectively for an emitter coverage of 80% independently of the cell contact strategy. A photocurrent loss about 1.3 mA/cm2 occurs when surface recombination velocity at the b-Si surfaces degrades from 6 cm/s to a final value of 28 cm/s.

28th European Photovoltaic Solar Energy Conference and Exhibition; 1135-1138, 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.

28th European Photovoltaic Solar Energy Conference and Exhibition; 1311-1316, 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.

28th European Photovoltaic Solar Energy Conference and Exhibition; 1213-1216, 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.

28th European Photovoltaic Solar Energy Conference and Exhibition; 1607-1610, 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.

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.

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.

—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

24th European Photovoltaic Solar Energy Conference, 21-25 September 2009, Hamburg, Germany; 1985-1991, In crystalline silicon (c-Si) solar cells based on p-type substrates, inversion layer emitters have been proposed as an alternative to high-temperature phosphorus diffusion. Dielectric film deposition at low temperature (≤ 400 ºC) is widely used for c-Si surface passivation and in this case emitters are induced by the positive fixed charge, Qf, at the c-Si/dielectric interface. In this work, we use 2-D simulations to explore solar cell structures with inversion layer emitters placed between local n+-emitters. The local diffusions could be defined by laser processing, resulting in potentially low-temperature processed structures. From simulation results, the low conductivity of inversion layer emitters obligates to short contact spacing and, hence, dense front grids and high shadow losses. However, placing the emitter at the back reduces these penalties, increasing the efficiency about 1% absolute. Furthermore, taking advantage of the fully metallized back surface, inversion layer emitters can be assisted by the workfunction difference between the c-Si substrate and the metal (typically aluminum) over the dielectric. As a result, the necessity of a high positive Qf value is relaxed.

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 Ωcm 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.

This paper studies the passivation of industrially textured deep silicon emitters using amorphous silicon carbonitride layers in stack configuration, deposited by plasma enhanced chemical vapor deposition. With this technique, emitter saturation current density can be decreased to values around 250 fA middot cm-2. As a consequence, open circuit voltages can be increased 25 mV achieving values around 640 mV.

28th European Photovoltaic Solar Energy Conference and Exhibition; 933-936, 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.

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.

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.

33rd European Photovoltaic Solar Energy Conference and Exhibition; 805-810, Reducing the wafer thickness for c-Si solar cell fabrication is an effective approach for cost-savings. Interdigitated Back Contacts (IBC) technology is a promising candidate to be applied to thin c-Si substrates due to its potential to facilitate thin device processing: thin c-Si solar cell could be processed attached to a glass with its rear surface, where all the contacts are to be defined, still accessible. The understanding of thin IBC c-Si solar cell performance has great significance in guiding the design of such devices. In this work, we explore the performance of thin IBC c-Si solar cells by both 3D TCAD device simulations and experimental fabrication based on conventional technology developed in our research group. On one hand, an optical model is proposed using 2D ray tracing method whose results are applied to 3D ATLAS TCAD simulator which is used to simulate the electrical performance of the devices. As a result, efficiencies in the range of 20 % are expected for substrates of 10-20 μm without changing our technology. On the other hand, a ~30 μm IBC solar cell is fabricated by thinning down a previously developed IBC c-Si solar cell on conventional thick high quality substrates demonstrating a 12.1% of efficiency. The front surface passivation provided by Al2O3 is deduced by comparing with the simulation results revealing a front surface recombination velocity of about 1500 cm/s.

© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. Dielectric/metal/dielectric structures based on vanadium pentoxide with a thin silver interlayer have been optimized to replace traditional transparent electrodes. As would be expected, there is a tradeoff in the metal thickness to achieve high transparency and low sheet resistance simultaneously. It has been demonstrated that an ultra-thin gold seed prevents the tendency of silver to form clusters. This wetting effect reduces the metal thickness needed to form a continuous film, which leads to a higher averaged transmittance and very low sheet resistance. On the other hand, vanadium pentoxide on silicon forms a high-quality hole-selective contact. Thus, these structures can be used as an all-in-one transparent electrode and selective contact for a new kind of heterojunction solar cells. This concept has been proved in a 13.3% efficient solar cell fabricated on n-type silicon wafers. Besides being dopant-free, the complete fabrication route did not require any sputtered transparent electrode.

Explore different materials as selective contacts in Germanium. The final objective is to fabricate a Germanium based solar cells usin selective contacts and low temperature processe. New materials are currently being studied in the field of photovoltaics to improve the efficiency and reduce fabrication costs. Among them, transition metal oxides have recently achieved competitive efficiencies as selective contacts on crystalline silicon solar cells, so the idea to expand them to other semiconductors came to mind. The goal of this project is to study the viability of these transition metal oxides based contacts on germanium substrates. Besides, an extensive lifetime study has been performed so as to adapt the equipment Sinton WCT-120 to germanium samples. Nuevos materiales están siendo estudiados en el campo fotovoltaico para mejorar la eficiencia y reducir costes de fabricación. Entre ellos, los óxidos de metales de transición han obtenido eficiencias competitivas como contactos selectivos en células de silicio cristalino, así que se planteó la idea de probar en otros semiconductores. El objetivo de este trabajo es estudiar la viabilidad de estos contactos basados en óxidos de metales de transición en sustratos de germanio. Aparte, se ha llevado a cabo un extenso estudio del tiempo de vida para adaptar el equipo Sinton WCT-120 a muestras de germanio. Nous materials estan sent estudiats en el camp fotovoltaic per tal de millorar l'eficiència i reduir costos de fabricació. Entre ells, els òxids de metalls de transició han obtingut eficiències competitives com a contactes selectius en cèl·lules de silici cristal·lí, així que es va plantejar la idea de provar en altres semiconductors. L'objectiu d'aquest treball és estudiar la viabilitat d'aquests contactes basats en òxids de metalls de transició en substrats de germani. A part, s'ha dut a terme un extens estudi del temps de vida per tal d'adaptar l'equip Sinton WCT-120 a mostres de germani.

III-IV semiconductors offer great potential due to their carrier mobility and direct bandgap, but their integration in Si wafers can be difficult due to lattice mismatch. Nanowire structures can solve this problem thanks to strain relaxation at the interface, as well as enhacing the functional properties of the III-IV semiconductor with respect to the bulk structure. Furthermore, MBE grown nanowires can be tuned in order to achieve quantum confinement, such as quantum wires and quantum dots, inside the nanowire structure, obtainig its consequently optical and electronical p In the aim to grow vertical self-catalyzed GaAs nanowires on [100] Si, fancy structures with a tapered shape resembling a tree were observed. They were called nanotrees. This is the first time that vertical growth has been achieved without catalyzer in this conditions. Different techniques were used to characterize these structures, such as TEM, Raman spectroscopy, photoluminescence and cathodoluminescence. Additionally, simulations were made to analyze light confinement inside the nanotree. Overall, nanotrees are promising structures for devices, from solar cells to photodiodes. Con el propósito de crecer nanohilos de arseniuro de galio en silicio [100] sin catalizador se descubrieron unas estructuras con forma triangular que se llamaron nanoárboles. Esta ha sido la primera vez que se ha obtenido un crecimiento vertical en estas condiciones. Diferentes técnicas se han utilizado para caracterizar estas estructuras, como TEM, espectroscopia de Raman, fotoluminiscencia y catodoluminiscencia. Adicionalmente, se hicieron simulaciones para analizar el confinamiento de la luz dentro del nanoárbol. En perspectiva, los nanoárboles son unas estructuras prometedoras para futuros dispositivos, como células solares o fotodiodos. Amb el propòsit de créixer nanofils d'arsenur de gal·li sobre silici [100] sense catalitzador es van descobrir unes estructures de forma triangular que es van anomenar nanoarbres. Aquest és el primer cop que s'assoleix un creixement vertical en aquestes condicions. Diferents tècniques s'han fet servir per caracteritzar aquestes estructures, com ara TEM, espectroscòpia de Raman, fotoluminescència i catodoluminescència. Addicionalment, es van fer simulacions per analitzar el confinament de la llum als nanoarbres. En perspectiva, els nanoarbres són unes estructures prometedores per a futurs dispositius, com ara cèl·lules solars o fotodíodes.

La tecnologia solar i fotovoltaica ha experimentat un important creixement durant els últims anys, i es preveu que sigui una de les principals fonts d'energia en un futur proper. Aquest creixement està relacionat amb una reducció significativa dels costos de producció i fabricació, així com amb una important evolució dels dispositius fotovoltaics que ha originat un increment en l'eficiència de les actuals cèl·lules solars. En el context del desenvolupament de nous dispositius fotovoltaics, la caracterització de materials es considera una tasca determinant. Així, tenint en compte que els dispositius fotovoltaics evolucionen cap a sistemes més prims i estructures més petites, les tècniques de caracterització d'alta resolució representen un paper rellevant en l'evolució i desenvolupament de la tecnologia solar i fotovoltaica. En el present treball, s’utilitzen diferents tècniques de caracterització d'alta resolució per estudiar determinades característiques de dispositius solars basats en silici cristal·lí. Entre les tècniques utilitzades trobem la microscòpia per sonda kelvin, l’espectroscòpia Raman i l’espectroscòpia de fotoluminescència. En concret, el treball es centra fonamentalment en l'estudi de capes de passivació superficial, així com en l'estudi de contactes elèctrics locals processats mitjançant tecnologia làser. L'elevada resolució de les tècniques de caracterització utilitzades en aquest treball ens permet accedir a informació única i exclusiva sobre certes propietats dels sistemes i materials estudiats. D'aquesta manera, la informació obtinguda representa la base per optimitzar i millorar els dispositius fotovoltaics actuals. En la part final del treball, les mateixes tècniques experimentals s'utilitzen per estudiar l'ordenament molecular de diferents capes orgàniques utilitzades en dispositius fotovoltaics d’última generació. Els sistemes fotovoltaics orgànics mostren atractives propietats com flexibilitat i baix cost, les quals posicionen a aquests sistemes com possibles candidats per un ampli ventall de noves aplicacions. Amb aquest últim estudi es vol demostrar la versatilitat i potencial de les tècniques experimentals utilitzades en aquest treball per a l'estudi de materials i dispositius fotovoltaics., Photovoltaic (PV) technology has experienced a tremendous growth during recent years, and PV energy is expected to be one of the main energy sources in the future. This growth has been induced by a drastic reduction of production costs, and an important evolution of solar cell technology that has lead to an increase of solar cells efficiency. In the context of device evolution, material and device characterization becomes an important task to further explore novel PV systems and architectures. Since ultimate PV technologies progressively move towards thinner devices and smaller structures, characterization techniques with high spatial resolution play an important role for the further technological development of the PV field. In this work, we apply different high-resolution advanced characterization techniques such as Kelvin Probe Force Microscopy (KPFM), micro-Raman and micro-Photoluminescence (PL) to carry out a comprehensive study of crystalline silicon (c-Si) PV devices. In particular, the work is focused on the analysis of rear surface passivation layers and local base contacts processed by laser, which are key features of ultimate c-Si PV architectures. The high-resolution capabilities of such experimental techniques allow obtaining unique and exclusive information about material properties and device operation. In this sense, the obtained information represents the foundations to improve and optimize the current PV devices and technology. In the final part of the work, we apply the same experimental techniques to study the molecular distribution across organic PV (OPV) thin films. OPV systems show attractive properties like low cost and flexibility, which make them suitable candidates for a broad range of novel application possibilities. With this last study we intend to demonstrate the versatility and applicability of the used characterization techniques for studying a wide range of PV materials and devices.

Treball final de màster oficial fet en col·laboració amb Universitat Autònoma de Barcelona (UAB), Universitat de Barcelona (UB) i Institut de Ciències Fotòniques (ICFO) [ANGLÈS] High efficiency Interdigitated back contact (IBC) solar cells help reduce the area of solar panels needed to supply sufficient amount of energy for household consumption. We believe that a properly passivated IBC cell with the aid of light trapping schemes can maintain an efficiency of 20% even with thickness under 20μm. In this work, photolithography and etching techniques are used for deep etching of crystalline Silicon (c-Si) wafer to a thickness less than 20 μm. Tetramethylammoniumhydroxide (TMAH) wet anisotropic etching and plasma based Reactive ion etching (RIE) are used with SPR 220-7.0 and SU-8 photoresists. SiO2 is used as making layer for TMAH etching. TMAH etch of a 4-inch c-Si wafer is done at a temperature of 80°C for 8 hours. RIE of a quarter of a 4-inch c-Si wafer is done for 3 hours using SF6 as reactive gas. A baseline photolithography process flow for SU-8 photoresist deposition was developed. The etch rates of TMAH etch techniques fall within the range of 0.3 – 0.45 μm/min and etch rates for Reactive ion etching fall within the range of 1.2 – 1.8 μm/min. The Reactive ion etching shows capability of achieving smaller thickness sizes with greater advantages than the TMAH etching technique. [CASTELLÀ] Alta eficiencia contacto posterior interdigitada (IBC) células solares ayudan a reducir el área de paneles solares necesarios para suministrar la suficiente cantidad de energía para el consumo doméstico. Creemos que una célula IBC correctamente pasivado con la ayuda de los esquemas de retención de la luz puede mantener una eficiencia del 20%, incluso con espesor bajo 20μm. En este trabajo, técnicas de fotolitografía y el grabado se utilizan para la profundidad de grabado de silicio cristalino (c-Si) oblea para un espesor inferior a 20 micras. Tetramethylammoniumhydroxide (TMAH) húmedo grabado anisotrópico y basado grabado iónico reactivo plasma (RIE) se utilizan con SPR 220-7,0 y SU-8 fotoresinas. SiO2 se utiliza como capa para hacer TMAH grabado. TMAH de grabado de un 4 pulgadas oblea de c-Si se realiza a una temperatura de 80°C durante 8 horas. RIE de un cuarto de 4 pulgadas c-oblea de Si se realiza durante 3 horas utilizando SF6 como gas reactivo. Se elaboró ​​un fotolitografía flujo del proceso de línea de base para el SU-8 fotoprotector deposición. Las velocidades de ataque de las técnicas de grabado TMAH caen dentro del rango de desde 0,3 hasta 0,45 micras/min y etch tarifas de caída grabado iónico reactivo dentro del rango de 1,3 hasta 1,8 micras/min. El grabado iónico reactivo muestra capacidad para conseguir grosores más pequeños con mayores ventajas que la técnica de grabado TMAH. [CATALÀ] Alta eficiència contacte posterior interdigitada (IBC) cèl·lules solars ajuden a reduir l'àrea de panells solars necessaris per subministrar la suficient quantitat d'energia per al consum domèstic. Creiem que una cèl·lula IBC correctament passivat amb l'ajuda dels esquemes de retenció de la llum pot mantenir una eficiència del 20%, fins i tot amb espessor baix 20μm. En aquest treball, tècniques de fotolitografia i el gravat s'utilitzen per a la profunditat de gravat de silici cristal (c-Si) hòstia per a un gruix inferior a 20 micres. Tetramethylammoniumhydroxide (TMAH) humit gravat anisotròpic i basat gravat iònic reactiu plasma (RIE) s'utilitzen amb SPR 220-7,0 i SU-8 fotoresines. SiO2 s'utilitza com a capa per fer TMAH gravat. TMAH de gravat d'un 4 polzades hòstia de c-Si es realitza a una temperatura de 80 ° C durant 8 hores. RIE d'un quart de 4 polzades c-hòstia de Si es realitza durant 3 hores utilitzant SF6 com a gas reactiu. Es va elaborar un fotolitografia flux del procés de línia de base per al SU-8 fotoprotector deposició. Les velocitats d'atac de les tècniques de gravat TMAH cauen dins del rang de des 0,3-0,45 micres / min i etch tarifes de caiguda gravat iònic reactiu dins del rang de 1,3-1,8 micres / min. El gravat iònic reactiu mostra capacitat per aconseguir gruixos més petits amb grans avantatges que la tècnica de gravat TMAH.

Treball final de màster oficial fet en col·laboració amb Universitat Autònoma de Barcelona (UAB), Universitat de Barcelona (UB) i Institut de Ciències Fotòniques (ICFO) [ANGLÈS] High efficiency Interdigitated back contact (IBC) solar cells help reduce the area of solar panels needed to supply sufficient amount of energy for household consumption. We believe that a properly passivated IBC cell with the aid of light trapping schemes can maintain an efficiency of 20% even with thickness under 20μm. In this work, photolithography and etching techniques are used for deep etching of crystalline Silicon (c-Si) wafer to a thickness less than 20 μm. Tetramethylammoniumhydroxide (TMAH) wet anisotropic etching and plasma based Reactive ion etching (RIE) are used with SPR 220-7.0 and SU-8 photoresists. SiO2 is used as making layer for TMAH etching. TMAH etch of a 4-inch c-Si wafer is done at a temperature of 80°C for 8 hours. RIE of a quarter of a 4-inch c-Si wafer is done for 3 hours using SF6 as reactive gas. A baseline photolithography process flow for SU-8 photoresist deposition was developed. The etch rates of TMAH etch techniques fall within the range of 0.3 – 0.45 μm/min and etch rates for Reactive ion etching fall within the range of 1.2 – 1.8 μm/min. The Reactive ion etching shows capability of achieving smaller thickness sizes with greater advantages than the TMAH etching technique. [CASTELLÀ] Alta eficiencia contacto posterior interdigitada (IBC) células solares ayudan a reducir el área de paneles solares necesarios para suministrar la suficiente cantidad de energía para el consumo doméstico. Creemos que una célula IBC correctamente pasivado con la ayuda de los esquemas de retención de la luz puede mantener una eficiencia del 20%, incluso con espesor bajo 20μm. En este trabajo, técnicas de fotolitografía y el grabado se utilizan para la profundidad de grabado de silicio cristalino (c-Si) oblea para un espesor inferior a 20 micras. Tetramethylammoniumhydroxide (TMAH) húmedo grabado anisotrópico y basado grabado iónico reactivo plasma (RIE) se utilizan con SPR 220-7,0 y SU-8 fotoresinas. SiO2 se utiliza como capa para hacer TMAH grabado. TMAH de grabado de un 4 pulgadas oblea de c-Si se realiza a una temperatura de 80°C durante 8 horas. RIE de un cuarto de 4 pulgadas c-oblea de Si se realiza durante 3 horas utilizando SF6 como gas reactivo. Se elaboró ​​un fotolitografía flujo del proceso de línea de base para el SU-8 fotoprotector deposición. Las velocidades de ataque de las técnicas de grabado TMAH caen dentro del rango de desde 0,3 hasta 0,45 micras/min y etch tarifas de caída grabado iónico reactivo dentro del rango de 1,3 hasta 1,8 micras/min. El grabado iónico reactivo muestra capacidad para conseguir grosores más pequeños con mayores ventajas que la técnica de grabado TMAH. [CATALÀ] Alta eficiència contacte posterior interdigitada (IBC) cèl·lules solars ajuden a reduir l'àrea de panells solars necessaris per subministrar la suficient quantitat d'energia per al consum domèstic. Creiem que una cèl·lula IBC correctament passivat amb l'ajuda dels esquemes de retenció de la llum pot mantenir una eficiència del 20%, fins i tot amb espessor baix 20μm. En aquest treball, tècniques de fotolitografia i el gravat s'utilitzen per a la profunditat de gravat de silici cristal (c-Si) hòstia per a un gruix inferior a 20 micres. Tetramethylammoniumhydroxide (TMAH) humit gravat anisotròpic i basat gravat iònic reactiu plasma (RIE) s'utilitzen amb SPR 220-7,0 i SU-8 fotoresines. SiO2 s'utilitza com a capa per fer TMAH gravat. TMAH de gravat d'un 4 polzades hòstia de c-Si es realitza a una temperatura de 80 ° C durant 8 hores. RIE d'un quart de 4 polzades c-hòstia de Si es realitza durant 3 hores utilitzant SF6 com a gas reactiu. Es va elaborar un fotolitografia flux del procés de línia de base per al SU-8 fotoprotector deposició. Les velocitats d'atac de les tècniques de gravat TMAH cauen dins del rang de des 0,3-0,45 micres / min i etch tarifes de caiguda gravat iònic reactiu dins del rang de 1,3-1,8 micres / min. El gravat iònic reactiu mostra capacitat per aconseguir gruixos més petits amb grans avantatges que la tècnica de gravat TMAH.

La solución de Mie a las ecuaciones de Maxwell describe la interacción de una onda luminosa con una esfera. Esta solución - para dimensiones de esfera comparables a la longitud de onda de la luz - tiene un resultado muy interesante. Para algunas frecuencias de resonancia y radios de la esfera, la sección de scattering puede ser más de diez veces mayor que la sección geométrica real. Además, en algunas condiciones, la sección de absorción también puede ser mayor que la real. Esto significaría que la microesfera absorbería más luz que la que incidía en su superficie. Esto tendría una consecuencia muy impresionante en el aprovechamento de la luz en placas solares. Para probar esta capacidad y aplicando la ley de Kirchhoff de radiación térmica - que establece que la emisividad es igual a la absorbancia - hemos de medir la radiación térmica de una sola microesfera. En este proyecto diseñamos un set-up óptico que formará parte de la configuración final utilizada para medir la radiación térmica de una sola microesfera. Para realizar la medición se utilizaron tecnicas de espectroscopia FT-IR combinada con técnicas de lock-in. Hemos podido medir un área de 10?m de radio en contraste con los pocos milímetros que el FT-IR normal mide. Mie’s solution to Maxwell’s equations describes the interaction of a light wave with a sphere. This solution - for sphere dimensions comparable to the light wavelength- has a very a interesting result. For some resonant frequencies and sphere radii, scattering section can be more than ten times greater than actual geometric section. Furthermore, under some conditions, the absorption cross section can also be larger than the real one. This means that the microsphere would absorb more light than the one impinging on its surface. This would have a very impressive consequence on light harvesting. In order to test this ability and applying Kirchho↵’s law of thermal radiation - which states that the emissivity is equal to the absorptivity - we would measure thermal radiation of a single microshpere. In this project we design a optical set-up that will be part of the final set-up used to measure the thermal radiation of a single microsphere. In order to perform the measurement Step-Scan FT-IR spectroscopy combined with lock-in techniques were used. We where able to measure an area of 10µm radius’ circle in contrast to the few millimetres that normal FT-IR measures.