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Electrodeposition is being investigated as an alternative method for developing large-area perovskite active layers for carbon-based solar cells. This study focuses on incorporating the 5-ammonium valeric acid iodide (5-AVAI) additive into the established MAPbI3perovskite. Previous research has shown that 5-AVAI can enhance the performance and stability of similar solar cells produced via spin-coating, drop-casting, or inkjet printing. However, its impact on solar cells with electrodeposited active layers remains unexplored. This research investigated the synthesis and characterization of mixed 3D–2D perovskites in the (MAPbI3)1–x((AVA)2PbI4)xfamily processed by electrodeposition. By varying both the conversion times and 5-AVAI concentrations, we analyzed the structural, optical, and photovoltaic properties of these novel perovskites. An intricate interplay between the conversion parameters and the perovskite properties is evident. Notably, photovoltaic devices with a specific quantity of 5-AVAI showed a 65% enhancement in the power conversion efficiency after 150 h of post-treatment at 40 °C under vacuum. These findings open the way to the improved performance of electrodeposited MAPbI3perovskites.

Hybrid organic–inorganic materials are a new class of materials used as interfacial layers (ILs) in polymer solar cells (PSCs). A hybrid material, composed of antimony as the inorganic part and diaminopyridine as the organic part, is synthesized and described as a new material for application as the electron extraction layer (EEL) in PSCs and compared to the recently demonstrated hybrid materials using bismuth instead of antimony. The hybrid compound is solution-processed onto the photoactive layer based on a classical blend, which is composed of a PTB7-Th low band gap polymer as the donor mixed with PC70BM fullerene as the acceptor material. By using a regular device structure and an aluminum cathode, the solar cells exhibited a power conversion efficiency of 8.42%, equivalent to the reference device using ZnO nanocrystals as the IL, and strongly improved compared to the bismuth-based hybrid material. The processing of extraction layers up to a thickness of 80 nm of such hybrid material reveals that the change from bismuth to antimony has strongly improved the charge extraction and transport properties of the hybrid materials. Interestingly, nanocomposites made of the hybrid material mixed with ZnO nanocrystals in a 1:1 ratio further improved the electronic properties of the extraction layers, leading to a power conversion efficiency of 9.74%. This was addressed to a more closely packed morphology of the hybrid layer, leading to further improved electron extraction. It is important to note that these hybrid EELs, both pure and ZnO-doped, also greatly improved the stability of solar cells, both under dark storage in air and under lighting under an inert atmosphere compared to solar cells treated with ZnO intermediate layers.

The encapsulation of organic photovoltaic (OPV) devices can help mitigate the degradation induced by environmental factors like water and oxygen and thus potential to increase OPV lifetime. Because flexibility is an important parameter for targeted OPV applications, this paper proposes a fundamental study on the impact of the roll-to-roll flexible encapsulation process. Both performance and mechanical reliability of encapsulated devices have been scouted. Furthermore, it has been demonstrated that a relatively simple peeling technique allows understanding the role of the interfaces inside a multilayered OPV device supported by a flexible poly(ethylene terephthalate) substrate. For this purpose, the peeling strengths between each layer were measured using a series of partial devices. This provided a quantitative analysis of the mechanical strength or quality of each interface. Two interfaces revealed pronounced weaknesses: active layer with hole transporting layer and transparent conducting electrode with electron transporting layer. Among various surface treatments applied to improve these interfaces, an optimized UV-ozone (UVO3) treatment proved to modify substantially the surface properties of used zinc oxide (ZnO) and thus improved its adhesion to the neighboring layers. The physicochemical and structural changes of ZnO have been confirmed by IR spectroscopy and contact angle measurements. It has also been shown that better interfaces within the device improve the overall performance of the devices and their resilience to roll-to-roll encapsulation.

Electrical stability and homogeneity of silver nanowire (AgNW) networks are critical assets for increasing their robustness and reliability when integrated as transparent electrodes in devices. Our ability to distinguish defects, inhomogeneities, or inactive areas at the scale of the entire network is therefore a critical issue. We propose one-probe electrical mapping (1P-mapping) as a specific simple tool to study the electrical distribution in these discrete structures. 1P-mapping has allowed us to show that the tortuosity of the voltage equipotential lines of AgNW networks under bias decreases with increasing network density, leading to a better electrical homogeneity. The impact of the network fabrication technique on the electrical homogeneity of the resulting electrode has also been investigated. Then, by combining 1P-mapping with electrical resistance measurements and IR thermography, we propose a comprehensive analysis of the evolution of the electrical distribution in AgNW networks when subjected to increasing voltage stresses. We show that AgNW networks experience three distinctive stages: optimization, degradation, and breakdown. We also demonstrate that the failure dynamics of AgNW networks at high voltages occurs through a highly correlated and spatially localized mechanism. In particular the in situformation of cracks could be clearly visualized. It consists of two steps: creation of a crack followed by propagation nearly parallel to the equipotential lines. Finally, we show that current can dynamically redistribute during failure, by following partially damaged secondary pathways through the crack.

Through a tight collaboration between chemical engineers, polymer scientists, and electrochemists, we address the degradation mechanisms of membrane electrode assemblies (MEAs) during proton exchange membrane fuel cell (PEMFC) operation in real life (industrial stacks). A special attention is paid to the heterogeneous nature of the aging and performances degradation in view of the hardware geometry of the stack and MEA. Macroscopically, the MEAis not fuelled evenly by the bipolar plates and severe degradations occur during start‐up and shut‐down events in the region that remains/becomes transiently starved in hydrogen. Such transients are dramatic to the cathode catalyst layer, especially for the carbon substrate supporting the Pt‐based nanoparticles. Another level of heterogeneity is observed between the channel and land areas of the cathode catalyst layer. The degradation of Pt3Co/C nanocrystallites employed at the cathode cannot be avoided in stationary operation either. In addition to the electrochemical Ostwald ripening and to crystallite migration, these nanomaterials undergo severe corrosion of their high surface area carbon support. The mother Pt3Co/C nanocrystallites are continuously depleted in Co, generating Co2+cations that pollute the ionomer and depreciate the performance of the cathode. Such cationic pollution has also a negative effect on the physicochemical properties of the proton‐exchange membrane (proton conductivity and resistance to fracture), eventually leading to hole formation. These defects were localized with the help of an infrared camera. The mechanical fracture‐resistance of various perfluorosulfonated membranes further demonstrated that polytetrafluoroethylene‐reinforced membranes better resist hole formation, due to their high resistance to crack initiation and propagation. WIREs Energy Environ2014, 3:540–560. doi: 10.1002/wene.113 This article is categorized under: Fuel Cells and Hydrogen > Science and MaterialsFuel Cells and Hydrogen > Systems and InfrastructureEnergy Research & Innovation > Science and Materials

PEMFC performances decay upon operation, following the degradation of their core materials. These degradations are heterogeneous within a PEMFC, whatever its operating conditions and its constitutive materials. Three distinct levels of degradation heterogeneities are observed in PEMFC cathodes. (i) The degradations are neither homogeneous along the gas channels of the bipolar plates (BP, from the inlet to the outlet), nor along the active layer thickness (from the membrane to the diffusion layer). (ii) The BP geometry also matters: repeated start/stop (fuel-starvation) events promote harsher degradation for the cathode regions facing the anode regions located under the BP land. (iii) Finally, the cells operate and age differently at the stack level. These degradations are strongly linked to the materials composing the MEA and the operating conditions, but also depend on the bipolar plates and stack design, which renders difficult any generalization of the conclusions obtained for a particular PEMFC test.