Indium tin oxide (ITO) and molybdenum are substrates of choice in the manufacture of the CdS-CIS photovoltaic cell, which is the base for the leading thin-film solar cell technology. Substantial advancement in this technology is expected if these devices can be made in nanoporous alumina (AAO) templates. The first step to this endeavor is to learn to form AAO templates on molybdenum and ITO substrates. This was accomplished, and the results are reported in this thesis. Starting substrates were glass, coated with either a thin molybdenum layer or a thin ITO layer. Aluminum was deposited on top of this conducting substrate. Oxalic acid was used as the electrolyte for anodization. In the case of molybdenum substrates, average pore diameter was 45 nm when an anodization voltage of 40 volts was used for approximately 46 minutes; current density was approximately 23 amps/sq. m. In the case of ITO substrates, pores of 45 nm diameter were obtained for approximately 20 minute anodization at 40 V; current density was 40 amps/sq. m; annealing of aluminum layer prior to anodization, at 550 oC (degrees Centigrade) for 90 minutes was needed to obtain good pores. A one micrometer thick CdS layer was electrodeposited inside the AAO pores on top of the ITO substrate. In preliminary experiments, CdS/Cu2S photovoltaic heterojunctions with an open circuit voltage of 242 mV were formed inside the nanopores.

Organic solar cells are cheaper and much easier to fabricate than the conventional inorganic solar cells, but they suffer from low efficiencies due to low carrier mobilities in organic films. In this study Copper Phthalocyanine (CuPc) and Buckminster Fullerene (C60) based Schottky diodes were fabricated on ITO coated glass substrates to study their performance and a study of the effect of thickness on the cell parameters of CuPc Schottky diodes was made. Also, TiO2 based devices were studied to see the effect of TiO2 layer on the cell parameters. The J-V curves were analyzed for series resistance, diode ideality factor and reverse saturation current density. The devices were also characterized by SEM and XRD measurements.

Silicon is the most important semiconducting material for optoelectronics owing to its suitable and tunable physical properties. Even though there are several alternatives, silicon based solar cells are still the most widely produced and commercially feasible system. Extensive efforts have been spent in order to increase the efficiency and decrease the cost of these systems. The studies that do not focus on replacement of the semiconducting material, mostly concentrate on the developments that could be brought by nanotechnological approaches. In this aspect, utilization of silicon nanowires has been predicted to improve the efficiency of the silicon based solar cell technology. Moreover, besides solar cells, silicon nanowires have been investigated for many other electronic systems such as thermoelectrics, light emitting diodes, biological/chemical sensors, photodetectors and lithium ion v batteries. Therefore, production of silicon nanowires through a cost-effective and well controlled method could make important contributions to many fields. In this thesis, electroless etching method, which is a novel and solution based method enabling vertically aligned silicon nanowire array fabrication over large areas, is investigated. A detailed parametric study resulting in a full control over the resultant nanowire morphology is provided. The parameters affecting the structure have been determined as etching time, solution temperature, solution concentration, pressure and starting wafer characteristics. The results show that electroless etching method could replace the conventional silicon nanowire fabrication methods. It was shown that specific nanowire lengths for any application, can be obtained simply by adjusting the parameters of electroless etching system. One of the most crucial features of vertically aligned silicon nanowire arrays is their remarkable antireflective properties. The optical reflectivity measurements showed that 42% reflectivity of pristine polished silicon wafer decreases down to 1% following fabrication of silicon nanowire arrays on their surface. This unique characteristic reveals that these nanowires could be used as antireflective surfaces in solar cells. Moreover, it was determined that p-n heterojunctions that are formed by silicon nanowires, namely radial heterojunctions, would yield higher efficiencies compared to planar heterojunctions because of the dramatic increase in the charge carrier collection efficiency and orthogonal photon absorption. On this subject, n-type silicon nanowire arrays were fabricated by electroless etching followed by drop casting Poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate) (PEDOT:PSS) organic layer on these nanowires as the complementary layer, forming the radial heterojunction. The energy conversion efficiency of silicon nanowire / PEDOT: PSS device was found as 5.30%, while planar silicon / PEDOT: PSS control device displayed only 0.62% efficiency. Developments and optimizations in both the electroless etching method and solar cell models could lead to important developments in photovoltaic industry.

Nano structured solar cells provide an opportunity for increased open circuit voltages and and short circuit currents in solar cells due to quantum confinement of the window and absorber materials and an increase in the optical path length for the incident light. In this study, both bulk and nano heterojunctions of CIS/CdS and Cu2S/CdS devices have been fabricated and studied on plain glass substrates and inside porous alumina templates to compare their performance. The devices have also been characterized SEM, XRD and JV measurements. The J-V curves have also been analyzed for series resistance, diode ideality factor and reverse saturation current density.

As aplicações dos dispositivos conversores de energia luminosa, principalmente da luz solar, em energia elétrica são muito variadas e com freqüência surge a possibilidade de uma nova aplicação. Muito tem sido discutido sobre aplicações de células solares em vestimentas, mochilas, tetos de estacionamentos e em embalagens eletrônicas. Esses tipos de aplicações não exigem dispositivos de alto desempenho, porém exigem que seja de baixo custo de processamento e, principalmente, que sejam flexíveis. Dispositivos fotovoltaicos flexíveis devem então ser fabricados por técnicas simples de processamento para permitir sua eventual produção em massa. Esse trabalho pretende dar uma contribuição na escolha dos materiais a serem usados em dispositivos fotovoltaicos flexíveis, focando seu desenvolvimento em células solares orgânicas de heterojunção de volume (BHJ), que são comumente processadas por solução. A estrutura escolhida foi a convencional de multicamadas onde o anodo transparente é o ITO (óxido de índio-estanho), seguida de uma camada transportadora de buracos (PEDOT:PSS), da camada ativa, e do cátodo, que em nosso caso foi formado por cálcio e alumínio, ambos depositados a vácuo. Como camada ativa, principal elemento de estudo nesse trabalho, foram estudados o P3HT:PC61BM, e o PTB7-Th:PC71BM, como elementos doador de elétrons (polímero) e aceitador de elétrons (derivado de fulereno). Em especial com o dispositivo fabricado com o PTB7-Th:PC71BM foi possível elaborar mudanças de processamento e assim melhorar consideravelmente a sua eficiência de conversão de potência. Em seguida, através de medidas de corrente-tensão (J-V) no escuro e sob iluminação, pudemos analisar a evolução dos parâmetros das células, como as resistências série (Rs) e paralelo (Rp), e também aqueles que definem a qualidade da célula solar: a corrente de curto-circuito (Jsc), a tensão de circuito aberto (Voc), o fator de preenchimento (FF), e a eficiência (η). Através dos ajustes das curvas J-V, no escuro e sob iluminação, usando expressões de J(V) extraídas de circuitos equivalentes, respectivamente, dos diodos e das células solares, pudemos realizar uma análise mais efetiva de como as resistências série e paralelo mudam com os elementos da camada ativa e também com diferentes processamentos. O fator de preenchimento (FF) é outro parâmetro importante que determina a eficiência de conversão de energia de uma célula solar orgânica, e existem vários fatores que podem influenciar significativamente o seu valor. Essa é uma das razões do porquê é difícil identificar a real origem desse parâmetro. Essa tese também deu elementos que correlacionam a estrutura química e morfológica da camada ativa com o fator de preenchimento. / The applications of light energy converters, especially the sunlight, in electrical energy are very varied and there is often the possibility of the appearance of new applications. Much has been discussed about solar cell applications in clothing, backpacks, parking ceilings and in electronic packaging. These types of applications do not require high-performance devices, but they do require low-cost processing and, above all, that they are flexible. Flexible photovoltaic devices must then be manufactured by simple processing techniques to allow their eventual mass production. This work intends to contribute to the choice of materials to be used in flexible photovoltaic devices, focusing their development on organic bulk heterojunction solar cells (BHJ), which are commonly processed via solution. The structure chosen for the device was the multilayer one, where the transparent anode is the ITO (indium- tin oxide), followed by a hole transport layer (PEDOT:PSS), the active layer, and the cathode, which in our case was formed by calcium and aluminum, both deposited under vacuum. As active layer, the main element of study in this work, we studied the P3HT: PC61BM and the PTB7-Th: PC71BM, as electron donor (polymer) and electron acceptor elements (derived from fullerene). In particular with the device made with the PTB7-Th:PC71BM it was possible to changes processing parameters and thus enhancing its power conversion efficiency. Then, through current-voltage measurements (J-V), in the dark and under illumination, we were able to analyze the evolution of the cell parameters, such as the series (Rs) and shunt (Rp) resistances, as well as those that define the solar cell quality: short-circuit current (Jsc), open-circuit voltage (Voc), fill factor (FF), and efficiency (η). Through the adjustments of the J-V curves, in the dark and under illumination, using J(V) expressions, for equivalent circuits of the diodes and solar cells respectively, we were able to perform a more effective analysis of how the series and shunt resistances change with the elements of the active layer and also with its processing. Fill factor (FF) is another important parameter that determines the energy conversion efficiency of an organic solar cell, and there are several factors that can significantly influence its value. This is one of the reasons why it is difficult to identify the true source of this parameter. This thesis also gave elements that correlate the chemical and morphological structure of the active layer with the fill factor.

Ce travail de thèse a pour but de comprendre l’impact des propriétés électriques du silicium cristallin sur les performances des cellules solaires Silicium à HétéroJonction (SHJ) et de déterminer des spécifications matériaux nécessaires en termes de durée de vie des porteurs de charge et de résistivité.Dans une première partie de cette thèse, le potentiel du silicium mono-like a été évalué pour la fabrication de cellules solaires SHJ. La forte productivité de cette technique permet de réduire considérablement les coûts de fabrication des plaquettes. Des rendements de conversion de 20% équivalents à ceux des matériaux du marché ont été obtenus ainsi qu’un rendement de 21.6% avec l’utilisation d’un procédé de fabrication de cellules haut rendements. Ces valeurs ont été obtenues pour des durées de vie volumiques moyennes sur les plaquettes supérieures à 1ms. Les principaux limitations de la qualité du matériau mono-like ont été identifiés. D’abord, la présence de zones multicristallines sur certaines plaquettes rend le matériau incomptable avec le procédé SHJ notamment en ce qui concerne les étapes de texturation des surfaces et ensuite l’uniformité en épaisseur des couches déposées. Ce type de défauts fait chuter en premier lieu la Jcc, puis la Vco et le FF et finalement le rendement de conversion. De plus, la présence de contamination et la génération de dislocations aux extrémités du lingot font également chuter la durée de vie volumique et les paramètres photovoltaïques des cellules. Finalement, seulement 30% de la hauteur de lingot a pu être utilisé pour des hauts rendements de conversion.La deuxième partie a été consacrée à l’étude et l’optimisation, avec la technologie SHJ, d’une technique de dopage innovante remplaçant celles utilisant des impuretés dopantes, telle que le phosphore, en générant des donneurs thermiques dans le substrat silicium cristallin. Cette méthode de dopage présente l’avantage d’utiliser l’oxygène naturellement présent dans le silicium en transformant en dopant par des recuits à 450°C. Cette technique est uniquement valable avec une procédé basse température tel que celui utilisé dans ce travail de thèse et permettrait de contrôler les propriétés électriques du silicium sur l’ensemble d’un lingot Cz afin d’augmenter le rendement matière. La compatibilité du silicium cristallin dopé par des DT a été validée pour une gamme de résistivité de 3-10Ω.cm et durées de vie volumique de 3-10ms. La limite d’utilisation des DT pour l’obtention de hauts rendements correspond à une concentration inférieure à 7x1014cm-3 (3Ω.cm, 3ms). La technique de dopage a été transférée avec succès à l’échelle du lingot et a permis d’obtenir de rendement de 20.7% avec un procédé industriel et même de 21.7% avec une métallisation « smart-wire ». Une perte de FF a été observée par rapport aux références, liées à une résistance série élevée dont l’origine n’a pas encore été confirmée mais dont la source la plus probable serait l’inhomogénéité radiale de résistivité générée par le dopage. / This study aims to understand the electrical properties impact of the crystalline Silicon on the HeteroJunction (SHJ) solar cells performances and define the required material specifications in terms of minority carrier lifetime and bulk resistivity.In the first part of this work, the potential of the mono-like silicon was evaluated for SHJ solar cells production The high productivity of the crystallization method allows to significantly reduce the material cost. 20% efficiencies comparable to reference wafers were obtained for industrial process and had reached 21.6% values have been reached with a high efficiency process. Values above 1ms bulk lifetime were mandatory to obtain these results. The main limitations of the material properties were identified. First, the presence of multicrystalline zones on the material is incompatible with the SHJ process especially regarding the texturization step and then layers thickness’ uniformity. This defects drive down, at the first order, the Jsc and then the Voc and FF. Moreover, the metallic contamination and the dislocations generation at the ingots ends induce also a bulk lifetime degradation and PV performances drop. Finally, only 30% of the ingot height was usable to obtain high solar cell efficiencies.In the second part of this work, an innovative doping method, replacing the ones which use doping impurities, such as phosphorus, by generating thermal donors (TD) was studied. The advantages of this doping method are to use the oxygen naturally content in the silicon to generate the doping after 450°C annealing. This method is only possible if low temperature solar cell process is performed such the one used in this work. It could control the electrical properties of the crystalline silicon throughout a complete Cz ingot and increase the material yield. For a resistivity range of 3-10Ω.cm and bulk lifetime between 3 and 10ms, the TD doped material is compatible with SHJ technology. The maximum TD concentration for a SHJ application was estimated to 7x1014cm-3.The doping method was successfully transferred to the ingot scale and allowed reaching 20.7% efficiency with an industrial process and 21.7% with the “smart-wire” improved metallization. A FF loss was observed compared to the references, related to high series resistances. The origin has not been confirmed yet, but the most likely source would be the radial resistivity inhomogeneity generated by doping on silicon bulk.

The present thesis is focused on rational design and synthesis of π-conjugated donoracceptor-donor (D-A-D) type oligomers and D-A type copolymers. Thesis is organized in seven chapters, apart from introduction remaining six chapters are grouped into two parts (A and B). Part A deals with Chapters 2, 3, 4 and Part B contains chapters 5, 6 and 7. A brief discussion on the content of individual chapters is provided below. Chapter 1 discusses the introduction to organic solar cell with operating principles and effect of spinodal decomposition on stability of the devices is presented. The status and literature related to the improvement of life time of the organic solar cells by self-assembly approach has been explored. In addition, design and synthesis of the fluorine substituted π-conjugated organic semiconductors for n-type OFETs and OLED has been discussed. Part A This part of the thesis attempt to address some of the challenges listed below (1) Investigation of miscibility of binary components in bulk heterojunction solar cells through H-bonding approach. (2) Synthesis of new low band gap molecular semiconductors having H-bonding sites. (3) Fabrication of bulk heterojunction solar cell devices using these new molecules and exploring the photovoltaics performance. Chapter 2, donor-acceptor-donor (D-A-D) concept has been employed to design low band gap oligomers named as TTB. Barbiturate functional group has been utilized to explore the concepts of supramolecular chemistry. It is shown that, TTB molecule self-organizes via intermolecular H-bonding between barbituric acid units. Interactions between the oligothiophene subunits were also found to be important, affording nanoribbons that were observed by atomic force and transmission electron microscopy. The applicability of TTB for organic electronic applications was investigated by fabricating organic field-effect transistors (OFETs) and organic photovoltaic device. The crystalline nanoribbons were beneficial in understanding the phase morphology of PCBM and TTB blend. Chapter 3, the self-assemble property of TTB was disrupted by the substitution of methyl group on the nitrogen of the barbituric acid moiety. The optical and electrochemical properties of the new derivative have been investigated by UV-Visible spectroscopy, photoluminescence spectroscopy and cyclic voltammetry. Further investigations on the effect of self-assembly on organic solar cells were carried out by fabricating BHJ and OFET. The results proved that the self-assembly within the donor moieties led to complete phase separation between the donor and acceptor which had an adverse effect on the photovoltaic performance. Chapter 4, the conjugation of TTB was extended by the synthesis of two new copolymers by polymerizing with two oliogothiophene (terthiophene and benzobithiophene) derivatives with different donating strength. The investigation of photophysical and electrochemical properties of copolymers were studied by varying the donating strength. As we increase the donating strength of oligothiophenes, the intramolecular charge transfer band of DA copolymers was red shifted. Further, density functional theory (DFT) calculation of these materials was carried out to get insight into their photophysical properties. Part B This part of the thesis attempt to address some of the challenges listed below (1) Investigation of fluorine substituted organic semiconductos like 2,2’ bithiazole and pheanthroimidazole. (2) Synthesis of pentafluoro phenyl appended derivatives of 2,2’ bithiazole and pheanthroimidazole. (3) Fabrication of OFETs and OLEDs using these new molecules and elucidated the device performance with molecular structure. Chapter 5, pentafluorophenyl appended 2,2’-bithiazole derivatives were synthesized. The single crystal x-ray diffraction studies shows the unusual strong type-II F•••F interactions within the distance of 2.668 Å, at an angle of 89.14° and 174.15°. It also shows the usual type-I F•••F interaction within the distance of 2.825Å, at an angle of 137.38° and 135.93°. Upon bromination type-II Br•••Br interaction was observed and the packing was further stabilized by S•••Br interactions. The conjugation was further extended with different aromatic and heteroaromatic substituents and synthesized the star shaped structure. The band gap as well as the electronic energy levels was tuned by substituting various aromatic and heteroaromatic substituents. These star shaped derivatives shows electron mobilities in the order of 10-4 to 10-3cm2/Vs. Chapter 6, Novel D-A copolymers were synthesized by Stille condensation of electron acceptor fluorinated phenanthroimidazole with electron donors like terthiophene and benzobithiophene. Prior to that insoluble pentafluoro phenyl phenanthroimidazole was Nalkylated in presence of DMF which concurrently resulted in C-F activation of the pentafluoro phenyl moiety. As we increase the donor strength from benzobithiophene to terthiophene the absorbance spectra was red shifted from 446 nm to 482 nm in solution and 455 nm to 484 nm in solid state. The band gap of these copolymers was found to be 2.4 eV for PIBDT and 2.2 eV for PIDHTT from the absorbance spectra. The photoluminescence data shows that these materials are promising for the yellow colour as well as orange colour displays, of narrow wavelength range (FWHM 40 nm for PIBDT and 35 nm for PIDHTT), which can be achieved just by the manipulation of donor moieties in the copolymers. The preliminary electroluminiscence data shows high brightness of 888cd/m2 (orange luminescence) for PIDHTT and 410cd/m2 (yellow luminescence) for PIBDT. Chapter 7, Acenaphtho[1,2-b]quinoxaline based donor–acceptor type low band gap conjugated copolymers were synthesized by Stille coupling reaction with the corresponding oligothiophene derivatives. The optical properties of the copolymers were characterized by ultraviolet-visible spectrometry while the electrochemical properties were determined by cyclic voltammetry. The band gap of these polymers was found to be in the range of 1.8-2.0 eV as calculated from the optical absorption band edge. The intense charge transfer band in absorption spectra shows the significant effect of acceptor in the copolymers. X-ray diffraction measurements show weak π–π stacking interactions between the polymer chains. The OFET devices fabricated using these co-polymers showed dominant p-channel transistor behavior with the highest mobility of 1×10-3cm2/Vs.

Les cellules photovoltaïques organiques ont fait l'objet d'un intérêt croissant au cours de ces dernières décennies car elles offrent un grand potentiel pour une production d'énergie renouvelable à faible coût. Afin d'obtenir des cellules solaires organiques à haut rendement de conversion d'énergie, beaucoup de recherches se focalisent sur les matériaux ayant des capacités à absorber la lumière efficacement. Dans ce contexte, le présent travail se concentre sur la conception et le développement de nouveaux matériaux donneurs d'électrons (oligomères et polymères) comme matériaux absorbant de la lumière basée sur l'approche « Donneur-Accepteur » alternant des segments riches en électron (donneur d'électron) et des unités pauvres en électron (accepteur d'électron). Trois séries d'unités riches en électron ont été étudiées: oligothiophènes, fluorène et indacenodithiophene. L'unité fluorénone est la principale unité « accepteur d'électron » étudiée. Une comparaison directe avec le système basé sur l'unité benzothiadiazole comme accepteur d'électron est également rapportée. Trois méthodes principales de synthèse ont été utilisées: polymérisation oxydante par le chlorure de fer (III), et les couplages croisés au palladium de type Suzuki ou de Stille. Les études spectroscopique UV-Visible en absorption et en photoluminescence sur ces oligomères et polymères ont démontré la présence de complexes à transfert de charges permettant d'élargir le spectre d'absorption. Les oligomères et les polymères possèdent des faibles largeurs de bande interdite de 1,6 eV à 2 eV. Les systèmes ayant des unités fluorénones présentent des spectres d'absorption étendus allant jusqu'à 600-700 nm, tandis que les systèmes ayant des unités benzothiadiazoles présentent des spectres d'absorption allant jusqu'à 700- 800 nm. La nature des bandes de complexes à transfert de charge se révèle d'être dépendant de la force de respective des unités « donneur d'électrons » et des unités « accepteur d'électrons ». Les niveaux d'énergies HOMO et LUMO des oligomères et les polymères sont déterminés par des mesures électrochimiques. Les polymères à base de fluorène possèdent des niveaux d'énergie HOMO les plus bas. Ces polymères testés en mélange avec les fullerenes PCBM en cellules photovoltaïques ont démontré des valeurs élevées de tension en circuit ouvert (Voc) proche de 0,9 V. Tous les oligomères et les polymères ont été testés dans des dispositifs photovoltaïques et ont montré des résultats encourageants avec des rendements de conversion allant jusqu'à 2,1 %. Ce sont des premièrs résultats obtenus après seulement quelques optimisations (ratios oligomères ou polymères : fullerènes et recuit thermique). Ce travail prometteur permet ainsi d'envisager des résultats plus élevés dans le futur. / Organic photovoltaic (OPV) cells have been a subject of increasing interest during the last decade as they are promising candidates for low cost renewable energy production. In order to obtain reasonably high performance organic solar cells, development of efficient light absorbing materials are of primary focus in the OPV field. In this context, the present work is focused on the design and development of new electron donor materials (oligomers and polymers) as light absorbing materials based on “Donor-Acceptor” approach alternating electron donating group and electron withdrawing group. Three main families of electron donating group are studied: oligothiophenes, fluorene and indacenodithiophene. Fluorenone unit is the principal electron withdrawing group studied and a direct comparison with the system based on benzothiadiazole unit as electron withdrawing unit is also provided. Three main synthetic methods were employed: oxidative polymerization mediated by Iron (III) chloride and Palladium cross-coupling reactions according to Suzuki coupling or Stille coupling conditions. Spectroscopic studies on absorption and photoluminescence have demonstrated the presence of characteristic charge transfer complex in all the studied D-A oligomers and polymers allowing the extension of the absorption spectrum. The D-A oligomers and polymers have shown an overall low optical band gap of 1.6-2 eV with absorption spectra up to 600 to 800 nm. The nature of the charge transfer complex transitions bands were found to be depending on the strength of the electron donating unit and the electron withdrawing unit. Furthermore molecular packing in solution and in solid state has also demonstrated to contribute to extension of absorption spectrum. The HOMO and LUMO energy levels of the oligomers and polymers were determined by electrochemical measurements. Fluorene-based polymers have shown low lying HOMO energy levels, and these polymers demonstrate high open circuit voltage (Voc) in photovoltaic cell when combined with fullerenes derivatives PCBM with Voc values close to 0.9 V. The oligomers and polymers tested in photovoltaic devices have shown promising results with the highest power conversion efficiency obtained of 2.1 % when combined with fullerenes PCBMC70. These results were obtained after only limited numbers of device optimizations such as the active materials ratios and thermal annealing. Therefore further optimization of devices may exhibit higher power conversion efficiencies.

La production durable d’énergie et la recherche d’alternatives aux sources non renouvelables font l’objet d’un grand intérêt à l’heure actuelle. Le principal objectif de cette thèse était de synthétiser et étudier de nouveaux complexes organométalliques à base de Ru-acétylure, puis évaluer leurs propriétés photovoltaïques dans des cellules solaires hybrides à colorant et organique à hétérojonction volumique. Des complexes bimétalliques dissymétriques ont été développés afin d’obtenir des chromophores à absorption panchromatique, en bénéficiant d’une structure « push-pull » et du motif [Ru(dppe)2] comme excellent relai d’électron. En parallèle des complexes symétriques à un ou deux centres métalliques ont été développés, ceux-ci ont ensuite été intégrés à des cellules solaires organiques à hétérojonction volumique. Lors de cette étude, chaque dispositif a fait l’objet de différentes étapes d’optimisations dans le but d’améliorer les transferts de charges en améliorant la morphologie de la couche active. Les principales méthodes d’optimisations appliquées ont consisté à réaliser des traitements par « solvent vapor annealing », ajouter des additifs structurants et utiliser le colorant dans une matrice polymère dans un dispositif à mélange ternaire. / Today the sustainable energy production and research for alternatives to non-renewable sources attract a lot of interest. The aim of this PhD research was to synthetize and study new organometallic complexes Ru-diacetylide based, then to characterize their photovoltaic properties in hybrid dye-sensitized and organic bulk-heterojunction solar cells. To obtain panchromatic chromophores, asymmetric bimetallic complexes have been designed using [Ru(dppe)2] unit as excellent electron relay in a “push-pull” structure. In parallel, symmetric complexes have been developed with one or two metallic centres, and then they have been integrated to organic bulk-heterojunction solar cells. For this study, each device has been optimized through different steps, in order to improve charges transfers by improving morphology of the active layer. The main methods of optimization applied consisted of application of “solvent vapor annealing” treatment, addition of structure additives and addition of the dye in polymer matrix, in ternary molecules blend device.

Die vorliegende Arbeit beschäftigt sich mit Ätzprozessen von alkalischen und insbesondere HF/HNO3-basierten Ätzmedien an Silicium (Si). Es wurden Ätzprozesse an kristallinen (c-Si) und besonders an amorph/kristallinen (a-Si:H/c-Si) Silicium-Strukturen mit Hilfe von in situ Photolumineszenz(PL)-Messungen untersucht. Diese ermöglichen eine Verfolgung der Veränderung der Grenzflächendefektdichte an der c-Si-Grenzfläche während der Ätzprozesse. Es wurde erstmals beobachtet, dass der über Ladungsträgerinjektion von Löchern in das Si ablaufende Ätzprozess in HNO3-reichen, HF/HNO3-basierten Ätzmedien eine temporäre Feldeffektpassivierung an der geätzten Grenzfläche verursacht, welche zu einer Verzögerung des eigentlichen Auflöseprozesses des Si führt. Die Anwendung dieser Ätzmedien erfolgte im Rahmen der Strukturierung von a-Si:H-Schichten auf c-Si zur Realisierung von interdigitierenden Kontaktstrukturen rückseitenkontaktierter a-Si:H/c-Si-Heterosolarzellen. Für diese Ätzprozesse konnte mit Hilfe von in situ PL-Messungen erstmalig eine in situ Prozesskontrolle etabliert werden. Der Ätzprozess kann exakt bei Erreichen der a-Si:H/c-Si-Grenzfläche gestoppt werden, wodurch die ätzbedingte Defektbildung an der resultierenden c-Si-Oberfläche minimiert wird. Als weiterer Themenschwerpunkt wurde eine Photolithographie-freie Nanostrukturierung von a-Si:H/c-Si-Strukturen durch metallkatalysiertes Ätzen (MAE) vorgestellt, wobei MAE erstmals auf a-Si:H angewandt wurde. Anhand von in situ PL-Messungen konnte ebenfalls eine, wenn auch geringere, Feldeffektpassivierung an der geätzten Grenzfläche im Zuge der Injektion von Löchern in das Si durch die katalytisch aktiven Ag Nanopartikel (AgNP) beobachtet werden. Mit den so steuerbaren MAE-Prozessen können a-Si:H-Schichten exakt bis zur a-Si:H/c-Si-Grenzfläche punktuell geöffnet werden. Auf diese Weise wurden p-Typ a-Si:H/c-Si-Heterosolarzellen mit einem punktförmigen Absorberkontakt erfolgreich realisiert. / This dissertation is concerned with wet chemical etching processes of silicon (Si) by alkaline and especially HF/HNO3 based etchants. The etching processes are applied to crystalline (c-Si) and amorphous/crystalline (a-Si:H/c-Si) samples and analyzed by in situ photoluminescence (PL) measurements. These measurements enable a monitoring of changes in the defect density at the c-Si interface during the etching processes. By etching of Si in HNO3-rich HF/HNO3 based etchants, a temporary field effect passivation at the etched c-Si surface by hole injection was established. It was detected by in situ PL measurements for the first time. This effect causes a delay of the actual dissolution of the Si. These etching processes were applied to structure a-Si:H layers on c-Si in order to establish interdigitated contacts for back contacted a-Si:H/c-Si heterojunction solar cells. A process control for that kind of etch back processes was developed for the first time by in situ PL measurements. This method enables an exact termination of the etching processes with the arrival of the etching front at the a-Si:H/c-Si interface. Thus, etching induced defects at the resulting c-Si surface can be reduced. Finally this thesis focuses on the development of a photolithography-free approach for nanostructuring of a-Si:H/c-Si samples using metal assisted etching (MAE). In this context, MAE was applied to a-Si:H for the first time. In situ PL measurements also showed a temporary field effect passivation during MAE due to hole injection by the catalytically active Ag nanoparticles (AgNP). Here, this effect was less distinct because of only punctual etching by the AgNP. These designed MAE processes are used to selectively etch a-Si:H layers exactly down to the a-Si:H/c-Si interface. This process opens new doors to a novel fabrication technique for point contacted heterojunction solar cells. P-type a-Si:H/c-Si heterojunction solar cells with point contacted back surface field are presented.