Water- and Heat-Activated Dynamic Passivation for Perovskite Photovoltaics

Further improvements in perovskite solar cells (PSCs) require better control of ionic defects in the perovskite photoactive layer during the manufacturing stage and their usage. Here, we report a living passivation strategy using a hindered urea/thiocarbamate bond Lewis acid-base material (HUBLA), where dynamic covalent bonds with water and heat-activated characteristics can dynamically heal the perovskite to ensure device performance and stability. Upon exposure to moisture or heat, HUBLA generates new agents and further passivates defects in the perovskite. Not only are the defects during the fabrication passivated, but new defects that evolve during the usage and operation of the device are passivated as well.<br/><br/>We prove the dynamic passivation ability of HUBLA, both chemically through X-ray photoelectron spectroscopy (XPS) and physically through photoluminescence (PL) maps of aged and pristine perovskite thin films. We determined the threshold for the water-activated passivation to be at 20% relative humidity, and for the heat-activated passivation, it is ≥ 55 °C. This dynamic passivation significantly improves the robustness of the treated perovskite thin films. For instance, at 85 °C in ambient air (~30% relative humidity), the perovskite thin film with HUBLA developed 2/3 less PbI₂ than the control film.<br/><br/>In devices, this passivation strategy achieved high-performance devices with a power conversion efficiency (PCE) of 25.1%. HUBLA devices retained 94% of their initial PCE for approximately 1500 hours of aging at 85 °C in N₂ under 1 sun illumination. Further devices with HUBLA maintained 88% of their initial PCE after 1000 hours of aging at 85 °C and 30% relative humidity (RH) in air under 1 sun. (1)<br/><br/>W.-T. Wang, P. Holzhey, N. Zhou, Q. Zhang et al., Water- and heat-activated dynamic passivation for perovskite photovoltaics. <i>Nature</i> (2024). https://doi.org/10.1038/s41586-024-07705-5