Days-Long Stable Bias-Free Solar Hydrogen Generation by Perovskite and Organic Photoanodes

Conversion of solar energy into hydrogen by photoelectrochemical water splitting is an emerging technology with large potential for sustainable green hydrogen generation. However, reaching the combination of high performance, stable and inexpensive photoelectrodes remains a scientific challenge. Solution-processable perovskite and organic photoactive materials have shown remarkable efficiency in solar cells, and they are extremely promising candidates for photoelectrochemical devices, but their application so far has been limited by their instability in aqueous media. In this presentation, we will show both perovskite and organic photoanodes applying NiFeOOH-functionalized self-adhesive graphite sheet, providing a simple, cost-effective approach to prevent degradation by the aqueous environment and eliminate almost all electrical losses between the photoactive layer and the water oxidation-catalyst.<br/><br/>The all-inorganic perovskite photoelectrodes incorporate solely Earth-abundant materials and apply a low annealing temperature carbon paste with tuned energy level CsPbBr₃photoactive layer. Controlling the perovskite phase by a facile chemical bath method allows to achieve a pure 3D CsPbBr₃ layer with 8.1 mA cm^-2 photocurrent density at +1.23 V_RHE (close to the radiative efficiency limit of CsPbBr₃) with record perovskite photoanode stability: 100% of stabilized photocurrent density maintained for more than 100 h. Devices with &gt;1 cm² area, and low-temperature processing will also be demonstrated.¹ We will also discuss our most recent results towards reaching bias-free water splitting with these CsPbBr₃ photoanodes by applying high porosity electrospun top electrode layers.<br/><br/>The polymer:non-fullerene acceptor containing organic (PM6:D18:L8-BO) photoanodes achieve breakthrough photocurrent densities over 25 mA cm^-2 at +1.23 V_RHE and remarkable, days-long operational stability. We will discuss strategies of how the continuous operation of the organic photoanode could be extended even further. Finally, polymer:polymer photoelectrodes, as well as monolithic organic tandem photoanodes (<i>i.e.</i>, two photoactive layers integrated into one photoanode to generate high photovoltage) with exceptionally low, negative onset potential and bias-free water splitting in two-electrode setup with solar-to-hydrogen efficiency reaching 5% will also be presented.<br/><br/><i>References: </i><br/>1. Daboczi, M. <i>et al.</i> Scalable All-Inorganic Halide Perovskite Photoanodes with &gt;100 h Operational Stability Containing Earth-Abundant Materials. <i>Advanced Materials</i> 2304350 (2023) doi:10.1002/ADMA.202304350.