Metal-halide perovskites have been widely investigated in the photovoltaic sector due to their promising optoelectronic properties and inexpensive fabrication techniques based on solution processing. Here we report the development of inorganic CsPbBr 3 -based photoanodes for direct photoelectrochemical oxygen evolution from aqueous electrolytes. We use a commercial thermal graphite sheet and a mesoporous carbon scaffold to encapsulate CsPbBr 3 as an inexpensive and efficient protection strategy. We achieve a record stability of 30 h in aqueous electrolyte under constant simulated solar illumination, with currents above 2 mA cm −2 at 1.23 V RHE . We further demonstrate the versatility of our approach by grafting a molecular Ir-based water oxidation catalyst on the electrolyte-facing surface of the sealing graphite sheet, which cathodically shifts the onset potential of the composite photoanode due to accelerated charge transfer. These results suggest an efficient route to develop stable halide perovskite based electrodes for photoelectrochemical solar fuel generation.

Metal halide perovskites (MHPs) constitute a rich library of materials with huge potential for disruptive optoelectronic technologies. Their main strength comes from the possibility of easily tuning their bandgap to integrate them in devices with different functionalities -in principle. In reality, this cannot be achieved yet. In fact, whereas defect tolerance can be claimed for MHPs with a bandgap of about 1.6 eV, the model system that is the object of intense investigations, MHPs with lower and higher bandgaps are far from being defect-tolerant. These materials show various forms of instabilities that are mainly driven by strong defect activity. Here we critically assess the most recent advances in elucidating the physical and chemical activity of defects in both high-bandgap and low-bandgap MHPs, while correlating it to performance and stability losses, especially for solar cells, the driving application for these materials. We also provide an overview of the strategies so far implemented to eventually overcome the remaining materials-based and device-based challenges.

Perovskite solar cells have gained increasing interest, especially after reaching performances which are comparable with mature silicon PV technologies. However, the perovskite crystalline structure CH 3 NH 3 PbI 3 is unstable in the presence of moisture, which leads to fast degradation under ambient conditions. The commercialisation of perovskite solar cells will only be achieved with the engineering of long term stable materials. We report a modified perovskite absorber layer obtained by adding methylammonium iodide (MAI) and tetrabutylammonium (TBA) iodide. The incorporation of TBA improves the film coverage, reducing the number of pinholes. X-ray diffraction analysis suggests that, in common with other mixed larger cation perovskites, two distinct phases coexist: a 3D perovskite material and a 2D layered material. The TBA containing perovskite films showed improved hydrophobicity, which contributed to significantly higher moisture stability. The cells maintained their original PCE after 45 days under ambient conditions without encapsulation. In comparison, the CH 3 NH 3 PbX 3 3D perovskite device lost more than 60% of its original efficiency over the same time.

Tin halide perovskites have recently emerged as promising materials for low bandgap solar cells. Much effort has been invested on controlling the limiting factors responsible for poor device efficiencies, namely...