We describe the degradation mechanism in a metallic nanowire network subjected to electrical stress. The nanowire network degradation is ascribed, at a very local scale, to hot-spot formation and the subsequent propagation of a spatially correlated disruptive crack.

The performance and stability in atmospheric conditions of organic photovoltaic devices can be improved by the integration of stable and efficient photoactive materials as substituent of the chemically unstable poly (3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS), generally used as organic hole transport layer. Promising candidates are p-type transparent conductive oxides, which combine good optoelectronic and a higher mechanical and chemical stability than the organic counterpart. In this work, we synthesize Cu-rich CuCrO₂ thin films by aerosol-assisted chemical vapour deposition as an efficient alternative to PEDOT:PSS. The effect of stoichiometry on the structural, electrical, and optical properties was analysed to find a good compromise between transparency, resistivity, and energy bands alignment, to maximize the photovoltaic performances., Average transmittance and bandgap are reduced when increasing the Cu content in these out of stoichiometry CuCrO₂ films. The lowest electrical resistivity is found for samples synthesized from a solution composition in the 60–70% range. The optimal starting solution composition was found at 65% of Cu cationic ratio corresponding to a singular point in Hackee’s figure of merit of 1 × 10⁻⁷ Ω⁻¹. PBDD4T-2F:PC₇₀BM organic solar cells were fabricated by integrating CuCrO₂ films grown from a solution composition ranging between 40% to 100% of Cu as hole transport layers. The solar cells integrating a film grown with a Cu solution composition of 65% achieved a power conversion efficiency as high as 3.1%, representing the best trade-off of the optoelectronic properties among the studied candidates. Additionally, despite the efficiencies achieved from CuCrO₂-based organic solar cells are still inferior to the PEDOT:PSS counterpart, we demonstrated a significant enhancement of the lifetime in atmospheric conditions of optimal oxides-based organic photovoltaic devices.

Nanostructuration of solar cells is an interesting approach to improve the photovoltaic conversion efficiency (PCE). This work aims at developing architectured 3D hybrid photovoltaic solar cells using ZnO nanowires (ZnONWs) as the electron transport layer (ETL) and nanocollectors of electrons within the active layer (AL). ZnONWs have been synthesized using a hydrothermal process with a meticulous control of the morphology. The AL of solar cells is elaborated using ZnONWs interpenetrated with a bulk heterojunction composed of donor (π-conjugate low band gap polymer: PBDD4T-2F)/acceptor (fullerene derivate: PC₇₁BM) materials. An ideal interpenetrating ZnONW-D/A system with predefined specific morphological characteristics (length, diameter, and inter-ZnONW distances) was designed and successfully realized. The 3D architectures based on dense ZnONW arrays covered with conformal coatings of AL result in an increased amount of the ETL/AL interface, enhanced light absorption, and improved charge collection efficiency. For AL/ZnONW assembly, spin-coating at 100 °C was found to be the best. Other parameters were also optimized such as the D/A ratio and the pre/post-treatments achieving the optimal device with a D/A ratio of 1.25/1 and methanol treated on ZnONWs before and after the deposition of AL. A PCE of 7.7% (1.4 times better than that of the 2D cells) is achieved. The improvement of the performances with the 3D architecture results from both of: (i) the enhancement of the ZnO/AL surface interface (1 μm²/μm² for the 2D structure to 6.6 μm²/μm² for the 3D architecture), (ii) the presence of ZnONWs inside the AL, which behave as numerous nanocollectors (∼60 ZnONW/μm²) of electrons in the depth of the AL. This result validates the efficiency of the concept of nanotexturing of substrates, the method of solar cell assembly based on the nano-textured surface, the chosen morphological characteristics of the nanotexture, and the selected photoactive organic materials.

This work aims at developing polymer surfaces with enhanced hydrophobicity by controlling both the surface chemistry and the surface structure. As a first step, a chemical surface modification is achieved by the incorporation of a synthetized tailored fluorinated copolymer, named POISE-a (Polymer prOcessing Interface StabilizEr), in a commercial polystyrene matrix. Then, a complementary physical approach based on micro-structuration of a polymer surface is used. Polystyrene films containing various contents of POISE-a were elaborated by a solvent casting method. The structuration of the films was conducted by replicating a texture from a nickel insert using a hot-embossing technique with optimized processing conditions. The beneficial effect of POISE-a on both the wettability properties and the replication efficiency was evaluated by the water/polymer static contact angle and the quantification of the replication rate, respectively. The use of this tailored additive, even at low percentages (i.e., 1 wt.%), associated with the structuration of the PS surface, improves both the hydrophobicity of polystyrene and the robustness of the replication process.