Since the discovery of transparent conducting oxide (TCO) thin films¡ATCO has been widely used in optoelectronic devices. To increase the potential application of the TCO, this study aims at growing amorphous TCO thin films which possess visible transparency and high electric conductivity. Up to date, only IGZO exhibits these properties. However, the nature resource of indium, the main material in IGZO, is rare and expensive. In this study, searching for new materials that do not contain In, while manifest high transparent and conductivity is our major challenge. ZnO has an energy band gap of 3.4eV, for which visible photon does not have enough energy to excite the electron in ZnO from the valence band to conduction band. Therefore, it reveals itself as transparent. ZnO materials are relative stable in high temperature and chemical environments and thus a good candidate for been developed into amorphous TCO. The reason for the high conductivity in amorphous IGZO thin films is because the S orbital of In is spherical symmetry and has large radius in which can overlap with the next In ions to form a continuous band for conduction. In this study, a similar strategy is employed by use of the large S orbital of the doping tin (Sn) in ZnO. A ceramic ZnO target for the pulse laser deposition system is partially wrapped with tin foil. The optimum growth condition are searching by tuning oxygen partial pressure, laser energy, the distance between the target and substrate, and substrate temperature.

Le photovoltaïque nécessite de nouveaux matériaux pour diminuer ces coûts et améliorer les rendements. Ces travaux de thèse ont concerné le développement de nouvelles phases d'oxyde de titane pour l'électronique transparente et la conversion de photon appliquée au PV silicium. L'ablation laser pulsé est une méthode de croissance particulièrement adaptée pour la prospection de matériaux aux propriétés innovantes. Le contrôle des phases anatase, rutile et d'une phase de composition TiO1.45 épitaxié en fonction de la pression partielle d'oxygène a permis de réaliser des films aux propriétés électriques, optiques innovantes. Un film biphasé anatase/rutile dopé niobium (TNO1.80) présente ainsi une transition métal-semi-conducteur aux alentours de 68K. Par ailleurs, le film de composition TiO1.45 épitaxié s'est révélé être un oxyde transparent conducteur de type p. La découverte de ce nouveau p-TCOs a été valorisée et validée par l'élaboration d'une homojonction p - n transparente. Les matrices d'oxyde de titane rutile et anatase ont également été utilisées pour accueillir des ions terres rares Ln3+ afin de convertir les photons ultra-violet du spectre solaire incident vers le proche infrarouge (800 > λ > 1100 nm). Le transfert d'énergie des matrices TiO2 vers les dopants Ln3+ a été étudié en fonction de la structure, de la quantité de dopant ainsi que la qualité de la microstructure des films dopés Ln3+ (Ln3+=Pr3+,Tm3+,Eu3+,Yb3+,Nd3+). / New materials are needed to decrease cost and improve photovoltaic cell performance. These thesis works are focused on the development of new titanium oxide phases for transparent electronic and photon conversion applied to silicon solar cell. Pulsed laser deposition is an adapted growth method for the prospection of materials with innovating properties. The control of epitaxial growth of anatase, rutile and a phase with a composition TiO1.45 in function of oxygen partial pressure allowed us to realize films with innovating electrical and optical properties. A two phase anatase/rutile film doped niobium (TNO1.80) have shown a metal-semiconductor transition about 68 K. Moreover, transparent TiO1.45 epitaxial thin film has displayed a p-type semiconduction behaviour which has been confirmed by the elaboration of a transparent p - n homojunction. Rutile and anatase titanium oxide matrix were also used to host rare earths ions in order to convert ultraviolet to near infra-red photon (800 > λ > 1100 nm). TiO2 matrix to dopant transfer has been studied in function of crystal structure, doping content and the quality of microstructure of films doped Ln3+(Ln3+=Pr3+,Tm3+,Eu3+,Yb3+,Nd3+).

In this thesis, we investigate the synthesis of CuAlO2 on sapphire (0001) substrate by rapid thermal annealing of an Al2O3/Cu2O/sapphire structure above 1000oC. We examine the effects of growth conditions on the structural, formation mechanism, and optical and electrical properties of CuAlO2 thin film. The film prepared at 1100 oC in air was with epitaxial structure as verified by X-ray diffraction methods. Gas ambient, temperature ramp rate and reaction temperature are crucial parameters for the formation of CuAlO2 film. We found that single-phase CuAlO2 thin films formed in air ambient by a rapid temperature ramp rate above 1000oC. A slow temperature ramp rate and a pure oxygen ambient might lead to the appearance of second phase such as CuAl2O4. Optical gap of our films were determined to be 3.75 eV. Optical transmittance depended on the temperature of thin film reaction. The best transmittance obtained was 60 % by annealing at 1100 oC in air. Photoluminescence and cathodoluminescence measurements showed that the two peaks obtained are around 3.4 eV and 1.8 eV corresponding to UV and red emission. As a result of CuAlO2 has an indirect gap about 1.8 eV. The electrical conductivity of the film related to the oxygen content was investigated by the annealing experiments in oxygen-deficient (vacuum) and oxygen-excess (air) ambient. The sheet resistance of CuAlO2 increases consistently with an increase in the duration of the vacuum annealing. Further annealing in air restores the sheet resistance to the original value. The highest conductivity obtained in this work was 0.57 S/cm. Metal contacts to CuAlO2 were also studied in this work. The current-voltage characteristics showed that Cu, Al, Ni or Au could form Ohmic contact to CuAlO2. The lowest contact resistance was using Al metal. However, when the contacts were post-annealed above 300oC, the contact resistance was increased.

GaInN has the potential to revolutionize the solar cell industry, enabling higher efficiency solar cells with its wide bandgap range spanning the entire solar spectrum. However, material quality issues stemming from the large lattice mismatch between its binary endpoints and questionable range of p-type doping has thus far prevented realization of high efficiency solar cells. Nonetheless, amorphous and multi-crystalline forms of GaInN have been theorized to exhibit a defect-free bandgap, enabling GaInN alloys at any indium composition to be realized. But the range of possible p-type doping has not yet been determined and no device quality material has been demonstrated thus far. Nonetheless, a Schottky barrier design (to bypass the p-type doping issue) on single-crystal GaInN can be used to provide some insight into the future of amorphous and micro-crystalline GaInN Schottky barrier solar cells. Through demonstration of a functional single crystalline GaInN Schottky barrier solar cell and comparison of the results to the best published reports for more conventional p-i-n GaInN solar cells, this work aims to establish the feasibility of amorphous and multi-crystalline GaInN solar cells. / Ph. D.

A novel lithographic fabrication method is used to fabricate nanopillars arrays of anisotropic Ag and TCO electrodes. Optical and electrical properties of the electrodes including bandgap, free carrier concentration, resistivity and surface plasmon frequency of different electrodes can be tuned by adjusting the dimensions and geometry of the pillars. Given the ability to tune the nonlocal responses of the plasmonic field enhancements, we attempt to determine the nature of the effective refractive index profile within the visible wavelength region for multi-layer hybrid nanostructures. Knowledge of the effective optical constants of the obtained structure is critical for various applications. nanopillars of TCO\Ag core shell structures have been successfully fabricated. The Maxwell-Garnett mixing law has been used to determine the optical constants of the nanostructure based on spectroscopic ellipsometry measurements. Simulated reflection spectra indicate a down shift in the Brewster angle of the pillars resulting from the reduction in the effective refractive index of the nanostructure. Two plasmonic resonances were observed, with one in the visible region and the other in the IR region. Plasmon hybridization model is used to describe the behavior of metal and metal oxide core shell nanostructured electrodes. Different charge density distributions around the pillars determine the plasma frequency which depends on the core and surrounding media dielectric constants. Finite Difference Time Domain (FDTD) simulation of different structures agree well with experiment and help us to understand electric field behavior at different structures with different geometries and dielectric constants. Plasmonic Ag nanopillar arrays are effective substrates for surface enhanced Raman spectroscopy (SERS). An enhancement factor up to 6 orders of magnitude is obtained. Monolayers of C60 is deposited on the Ag nanopillars and the interface of C60/Ag is studied which is important in optoelectronic devices. Electron delocalization between C60 and Ag is confirmed.

abstract: Nanoporous electrically conducting materials can be prepared with high specific pore volumes and surface areas which make them well-suited for a wide variety of technologies including separation, catalysis and owing to their conductivity, energy related applications like solar cells, batteries and capacitors. General synthetic methods for nanoporous conducting materials that exhibit fine property control as well as facility and efficiency in their implementation continue to be highly sought after. Here, general methods for the synthesis of nanoporous conducting materials and their characterization are presented. Antimony-doped tin oxide (ATO), a transparent conducting oxide (TCO), and nanoporous conducting carbon can be prepared through the step-wise synthesis of interpenetrating inorganic/organic networks using well-established sol-gel methodology. The one-pot method produces an inorganic gel first that encompasses a solution of organic precursors. The surface of the inorganic gel subsequently catalyzes the formation of an organic gel network that interpenetrates throughout the inorganic gel network. These mutually supporting gel networks strengthen one another and allow for the use of evaporative drying methods and heat treatments that would usually destroy the porosity of an unsupported gel network. The composite gel is then selectively treated to either remove the organic network to provide a porous inorganic network, as is the case for antimony-doped tin oxide, or the inorganic network can be removed to generate a porous carbon material. The method exhibits flexibility in that the pore structure of the final porous material can be modified through the variation of the synthetic conditions. Additionally, porous carbons of hierarchical pore size distributions can be prepared by using wet alumina gel as a template dispersion medium and as a template itself. Alumina gels exhibit thixotropy, which is the ability of a solid to be sheared to a liquid state and upon removal of the shear force, return to a solid gel state. Alumina gels were prepared and blended with monomer solutions and sacrificial template particles to produce wet gel composites. These composites could then be treated to remove the alumina and template particles to generate hierarchically porous carbon. / Dissertation/Thesis / Ph.D. Chemistry 2012

Functional materials are essential to human welfare and to provide foundations for emerging industries. As an alternative route to experimental materials discovery, computational materials designs are playing an increasingly significant role in the whole discovery process. In this work, we use an in-house developed python utility: PAOFLOW, which generates finite basis Hamiltonians from the projection of first principles plane-wave pseudopotential wavefunctions on pseudo atomic orbitals(PAO) for post-process calculation on various properties such as the band structures, density of states, complex dielectric constants, diffusive and anomalous spin and charge transport coefficients. In particular, we calculated the dielectric function of Sr-, Pb-, and Bi-substituted BaSnO3 over wide concentration ranges. Together with some high-throughput experimental study, our result indicates the importance of considering the mixed-valence nature and clustering effects upon substitution of BaSnO3 with Pb and Bi. We also studied two prototype ferroelectric rashba semiconductors, GeTe and SnTe, and found the spin Hall conductivity(SHC) can be large either in ferroelectric or paraelectric structure phase. Upon doping, the polar displacements in GeTe can be sustained up to a critical hole concentration while the tiny distortions in SnTe vanish at a minimal level of doping. Moreover, we investigated the sensitivity of two dimensional group-IV monochalcogenides to external strain and doping, which reveal for the first time giant intrinsic SHC in these materials, providing a new route for the design of highly tunable spintronics devices based on two-dimensional materials.

Photovoltaic technologies use light from the sun to create electricity, using a wide range of materials and mechanisms. The generation of clean, renewable energy using this technology must become price competitive with conventional power generation if it is to succeed on a large scale. The field of photovoltaics can be split into many sub-groups, however the overall aim of each is to reduce the cost per watt of the produced electricity. One such solar cell which has potential to reduce the cost significantly is the dye sensitised solar cell (DSC), which utilises cheap materials and processing methods. The reduction in cost of the generated electricity is largely dependent on two parameters. Firstly, the efficiency that the solar cell can convert light into electricity and secondly, the cost to deposit the solar cell. This thesis aims to address both factors, specifically looking at altering the transparent conducting oxide (TCO) and substrate in the solar cell. One method to improve the overall conversion efficiency of the device is to implement the DSC as the top cell in a tandem structure, with a bottom infra-red absorbing solar cell. The top solar cell in such a structure must not needlessly absorb photons which the bottom solar cell can utilise, which can be the case in solar cells utilising standard transparent contacts such as fluorine-doped tin oxide. In this work, transparent conducting oxides with high mobility such as titanium-doped indium oxide (ITiO) have been used to successfully increase the amount of photons through a DSC, available for a bottom infra-red sensitive solar cell such as Cu(In,Ga)Se2 (CIGS). Although electrically and optically of very high quality, the production of DSCs on this material is difficult due to the heat and chemical instability of the film, as well as the poor adhesion of TiO2 on the ITiO surface. Deposition of a interfacial SnO2 layer and a post-deposition annealing treatment in vacuum aided the deposition process, and transparent DSCs of 7.4% have been fabricated. The deposition of a high quality TCO utilising cheap materials is another method to improve the cost/watt ratio. Aluminium-doped zinc oxide (AZO) is a TCO which offers very high optical and electronic quality, whilst avoiding the high cost of indium based TCOs. The chemical and thermal instability of AZO films though present a problem due to the processing steps used in DSC fabrication. Such films etch very easily in slightly acidic environments, and are susceptible to a loss of conductivity upon annealing in air, so some steps have to be taken to fabricate intact devices. In this work, thick layers of SnO2 have been used to reduce the amount of etching on the surface of the film, whilst careful control of the deposition parameters can produce AZO films of high stability. High efficiency devices close to 9% have been fabricated using these stacked layers. Finally, transferring solar cells from rigid to flexible substrates offers cost advantages, since the price of the glass substrate is a significant part of the final cost of the cell. Also, the savings associated with roll to roll deposition of solar cells is large since the production doesn't rely on a batch process, using heavy glass substrates, but a fast, continuous process. This work has explored using the high temperature stable polymer, polyimide, commonly used in CIGS and CdTe solar cells. AZO thin films have been deposited on 7.5um thick polyimide foils, and DSCs of efficiency over 4% have been fabricated on the substrates, using standard processing methods.

L'électronique transparente est actuellement limitée par la difficulté de construire une jonction p-n transparente, en raison du manque d'oxyde transparent conducteur (TCO) de type p réellement performant. L'oxyde cuivreux Cu2O est un TCO de type p prometteur, mais sa bande interdite relativement étroite pour un TCO (2,1 eV), limite sa transmittance dans le domaine visible. Dans le cadre de cette thèse, nous cherchons à augmenter cette valeur. Pour cela, nous explorons la méthode MOCVD comme technique de dépôt pour le dopage au strontium et au calcium de l’oxyde cuivreux. Ce dopage est supposé élargir la bande interdite du Cu2O d'après des calculs ab initio effectués à l'institut Tyndall, à Cork. Dans le chapitre I, nous présentons le contexte de cette thèse. Après avoir expliqué les conditions que doit remplir un matériau pour être un TCO de type p, nous présentons l'état de l'art concernant le Cu2O. Dans le chapitre II, nous présentons l'ensemble des techniques utilisées dans le cadre de cette thèse, de l'élaboration (MOCVD, recuits thermiques) à la caractérisation (MEB, MET, AFM, DRX, spectroscopie FTIR, spectroscopie Raman, XPS, spectroscopie UV-vis-NIR, mesures 4 pointes et mesures d'effet Hall). Au cours du chapitre III, l'influence des paramètres de la MOCVD sur la composition et la morphologie a été analysée pour l’élaboration de couches de Cu2O pures, non dopées en vue d'établir les conditions optimales de dépôt. Nous obtenons des couches continues sur substrat de Si/SiO2, alors qu'elles sont systématiquement hétérogènes avec des zones sans dépôt sur silicium. En outre, nous mettons en évidence le risque d'obtenir la phase cuivre métallique lorsque la concentration de précurseur est élevée, la pression partielle d'oxygène faible et/ou la température élevée. Partant de ces conditions optimales, nous étudions dans le chapitre IV l'influence du dopage au strontium sur les propriétés fonctionnelles des couches (résistivité, largeur de bande interdite et transmittance dans le visible). Une chute de la résistivité a été observée lors du dopage au strontium. Les couches non dopées ont des résistivités de l'ordre de 103 Ω.cm ou plus, contre 10 Ω.cm pour les couches contenant entre 6 et 15% de strontium. La conductivité est bien de type p avec une mobilité de l’ordre de 10 cm2.V-1.s-1 et une densité de porteur de quelques 1016 cm-3. L’écart très grand entre cette densité de porteur et la teneur globale en Sr est lié à la présence d’une contamination des couches par du carbonate et du fluorure de strontium mis en évidence par FTIR et XPS. L’influence réelle de ces impuretés n’a pu être déterminée. Enfin il n'a pas été constaté de variation significative des propriétés optiques, la bande interdite restant large d'environ 2,4 eV et la transmittance moyenne entre 500 et 1000 nm de l'ordre de 55%. Des tendances similaires sont observées dans le chapitre V qui aborde le dopage au calcium, avec comme particularité le fait pour un fort taux de dopage et sous assistance UV, d'aboutir à la présence d'espaces vides localisés à l'interface substrat/Cu2O qui pourrait être lié à la décomposition du carbonate de calcium. Finalement, nous procédons à des recuits thermiques des couches, dopées ou non, dans le chapitre VI. Pour les couches non dopées, cela permet de diminuer la résistivité jusqu’à des valeurs de 10-100 Ω.cm. Pour les couches dopées, cela permet aux couches ayant une résistivité initiale de 10 Ω.cm de descendre jusqu'à 1 Ω.cm. Au cours de cette thèse, nous avons établi les effets du dopage au Sr ou Ca qui conduisent à une forte chute de résistivité sans impact sur les propriétés optiques à la différence des résultats prévus par les calculs ab initio. Nous sommes ainsi parvenus à améliorer les propriétés des couches Cu2O transparentes de type p. / Transparent electronic is currently limited by the lack of a really performant p-type transparent conducting oxide (TCO), which makes the elaboration of a transparent p-n junction challenging. Cuprous oxide Cu2O is a promising p-type TCO, but its optical transmittance in the visible spectrum is limited by its relatively low band gap (2.1 eV). In this thesis, we aim at increasing this value. To achieve that, we explore MOCVD as the growth method for strontium and calcium doping of cuprous oxide. According to ab-initio calculations performed at Tyndall Institute in Cork, doping with these elements is supposed to increase the band gap of Cu2O. In chapter I, we introduce the context of this thesis. After explaining the required conditions that a material must fulfil to be a p-type TCO, we present the state of the art of Cu2O. In chapter II, we present all the techniques used in this work, from the elaboration (MOCVD, thermal annealing) to characterization (SEM, TEM, AFM, XRD, FTIR, Raman spectroscopy, XPS, UV-vis-NIR spectroscopy, 4 point probe and Hall effect measurement). In chapter III, our objective is to synthesize pure, undoped Cu2O thin films. We explore the influence of the MOCVD parameters on the films composition and morphology. We get homogenous films on Si/SiO2 substrates, while we get heterogeneous films with un-deposited parts on silicon substrate. In addition, we show the risk to get the metallic copper phase when precursor concentration is high, oxygen partial pressure is low, and/or temperature is high. This enables us to determine the optimal deposition conditions. Starting from those optimal conditions, we study the influence of strontium doping on the functional properties of the films (resistivity, band gap and visible light transmittance) in chapter IV. A decrease of resistivity was observed with strontium doping. While undoped films show resistivity values of 103 Ω.cm or more, films doped from 6 to 15% strontium show resistivity values of about 10 Ω.cm. P-type conductivity was confirmed through Hall effect measurements, with a mobility close to 10 cm2.V-1.s-1 and a charge carrier density of about 1016 cm-3. The large difference between this carrier density and the Sr concentration can be linked with the presence of a strontium carbonate and fluoride contamination that was detected by FTIR and XPS. The exact influence of those impurities is not well known. In addition, no significant variation of optical properties was observed, the band gap remained close to 2.4 eV and average transmittance in the 500-1000 nm range was about 55%. Similar tendencies were observed for calcium doping, addressed in chapter V. Calcium doping showed the particularity of leading to the presence of cavities localized at the substrate/Cu2O interface, for a high dopant concentration and under UV assistance. Eventually, we performed thermal annealing on some samples, doped and undoped, in chapter VI. For undoped samples, it allowed to decrease resistivity in the 10-100 Ω.cm range. For doped samples, it allows samples showing initial resistivity of about 10 Ω.cm to decrease it to 1 Ω.cm. No impact of thermal annealing on sample morphology or composition was observed. In this thesis, we successfully established the effects of Sr or Ca doping, which lead to a significant decrease of the resistivity without impact on the optical properties, unlike what was predicted by the ab initio calculations. We were thus able to improve the p-type transparent Cu2O thin films properties.

L'électronique transparente est actuellement limitée par la difficulté de construire une jonction p-n transparente, en raison du manque d'oxyde transparent conducteur (TCO) de type p réellement performant. L'oxyde cuivreux Cu2O est un TCO de type p prometteur, mais sa bande interdite relativement étroite pour un TCO (2,1 eV), limite sa transmittance dans le domaine visible. Dans le cadre de cette thèse, nous cherchons à augmenter cette valeur. Pour cela, nous explorons la méthode MOCVD comme technique de dépôt pour le dopage au strontium et au calcium de l’oxyde cuivreux. Ce dopage est supposé élargir la bande interdite du Cu2O d'après des calculs ab initio effectués à l'institut Tyndall, à Cork. Dans le chapitre I, nous présentons le contexte de cette thèse. Après avoir expliqué les conditions que doit remplir un matériau pour être un TCO de type p, nous présentons l'état de l'art concernant le Cu2O. Dans le chapitre II, nous présentons l'ensemble des techniques utilisées dans le cadre de cette thèse, de l'élaboration (MOCVD, recuits thermiques) à la caractérisation (MEB, MET, AFM, DRX, spectroscopie FTIR, spectroscopie Raman, XPS, spectroscopie UV-vis-NIR, mesures 4 pointes et mesures d'effet Hall). Au cours du chapitre III, l'influence des paramètres de la MOCVD sur la composition et la morphologie a été analysée pour l’élaboration de couches de Cu2O pures, non dopées en vue d'établir les conditions optimales de dépôt. Nous obtenons des couches continues sur substrat de Si/SiO2, alors qu'elles sont systématiquement hétérogènes avec des zones sans dépôt sur silicium. En outre, nous mettons en évidence le risque d'obtenir la phase cuivre métallique lorsque la concentration de précurseur est élevée, la pression partielle d'oxygène faible et/ou la température élevée. Partant de ces conditions optimales, nous étudions dans le chapitre IV l'influence du dopage au strontium sur les propriétés fonctionnelles des couches (résistivité, largeur de bande interdite et transmittance dans le visible). Une chute de la résistivité a été observée lors du dopage au strontium. Les couches non dopées ont des résistivités de l'ordre de 103 Ω.cm ou plus, contre 10 Ω.cm pour les couches contenant entre 6 et 15% de strontium. La conductivité est bien de type p avec une mobilité de l’ordre de 10 cm2.V-1.s-1 et une densité de porteur de quelques 1016 cm-3. L’écart très grand entre cette densité de porteur et la teneur globale en Sr est lié à la présence d’une contamination des couches par du carbonate et du fluorure de strontium mis en évidence par FTIR et XPS. L’influence réelle de ces impuretés n’a pu être déterminée. Enfin il n'a pas été constaté de variation significative des propriétés optiques, la bande interdite restant large d'environ 2,4 eV et la transmittance moyenne entre 500 et 1000 nm de l'ordre de 55%. Des tendances similaires sont observées dans le chapitre V qui aborde le dopage au calcium, avec comme particularité le fait pour un fort taux de dopage et sous assistance UV, d'aboutir à la présence d'espaces vides localisés à l'interface substrat/Cu2O qui pourrait être lié à la décomposition du carbonate de calcium. Finalement, nous procédons à des recuits thermiques des couches, dopées ou non, dans le chapitre VI. Pour les couches non dopées, cela permet de diminuer la résistivité jusqu’à des valeurs de 10-100 Ω.cm. Pour les couches dopées, cela permet aux couches ayant une résistivité initiale de 10 Ω.cm de descendre jusqu'à 1 Ω.cm. Au cours de cette thèse, nous avons établi les effets du dopage au Sr ou Ca qui conduisent à une forte chute de résistivité sans impact sur les propriétés optiques à la différence des résultats prévus par les calculs ab initio. Nous sommes ainsi parvenus à améliorer les propriétés des couches Cu2O transparentes de type p. / Transparent electronic is currently limited by the lack of a really performant p-type transparent conducting oxide (TCO), which makes the elaboration of a transparent p-n junction challenging. Cuprous oxide Cu2O is a promising p-type TCO, but its optical transmittance in the visible spectrum is limited by its relatively low band gap (2.1 eV). In this thesis, we aim at increasing this value. To achieve that, we explore MOCVD as the growth method for strontium and calcium doping of cuprous oxide. According to ab-initio calculations performed at Tyndall Institute in Cork, doping with these elements is supposed to increase the band gap of Cu2O. In chapter I, we introduce the context of this thesis. After explaining the required conditions that a material must fulfil to be a p-type TCO, we present the state of the art of Cu2O. In chapter II, we present all the techniques used in this work, from the elaboration (MOCVD, thermal annealing) to characterization (SEM, TEM, AFM, XRD, FTIR, Raman spectroscopy, XPS, UV-vis-NIR spectroscopy, 4 point probe and Hall effect measurement). In chapter III, our objective is to synthesize pure, undoped Cu2O thin films. We explore the influence of the MOCVD parameters on the films composition and morphology. We get homogenous films on Si/SiO2 substrates, while we get heterogeneous films with un-deposited parts on silicon substrate. In addition, we show the risk to get the metallic copper phase when precursor concentration is high, oxygen partial pressure is low, and/or temperature is high. This enables us to determine the optimal deposition conditions. Starting from those optimal conditions, we study the influence of strontium doping on the functional properties of the films (resistivity, band gap and visible light transmittance) in chapter IV. A decrease of resistivity was observed with strontium doping. While undoped films show resistivity values of 103 Ω.cm or more, films doped from 6 to 15% strontium show resistivity values of about 10 Ω.cm. P-type conductivity was confirmed through Hall effect measurements, with a mobility close to 10 cm2.V-1.s-1 and a charge carrier density of about 1016 cm-3. The large difference between this carrier density and the Sr concentration can be linked with the presence of a strontium carbonate and fluoride contamination that was detected by FTIR and XPS. The exact influence of those impurities is not well known. In addition, no significant variation of optical properties was observed, the band gap remained close to 2.4 eV and average transmittance in the 500-1000 nm range was about 55%. Similar tendencies were observed for calcium doping, addressed in chapter V. Calcium doping showed the particularity of leading to the presence of cavities localized at the substrate/Cu2O interface, for a high dopant concentration and under UV assistance. Eventually, we performed thermal annealing on some samples, doped and undoped, in chapter VI. For undoped samples, it allowed to decrease resistivity in the 10-100 Ω.cm range. For doped samples, it allows samples showing initial resistivity of about 10 Ω.cm to decrease it to 1 Ω.cm. No impact of thermal annealing on sample morphology or composition was observed. In this thesis, we successfully established the effects of Sr or Ca doping, which lead to a significant decrease of the resistivity without impact on the optical properties, unlike what was predicted by the ab initio calculations. We were thus able to improve the p-type transparent Cu2O thin films properties.