Composites of cross-linked perovskite/polymer with sodium borate for efficient and stable perovskite solar cells

Although perovskite solar cells have been widely investigated to improve the photovoltaic conversion efficiency so far, perovskite light absorbers have a severe disadvantage for commercialization due to their facile degradation when exposed to humidity and oxygen. Herein, we suggest a synergic anti-solvent dripping strategy to improve the performance and stability of a photovoltaic device using a mixture of PMMA/sodium borate salt (borax) and perovskite materials. We characterized its unique features, i.e., the enhanced hydrogen bond formation between the PMMA/sodium borate mixture and the perovskite light absorber, which induced the lateral grain growth of perovskite films and efficient passivation of the surface and grain boundaries. Consequently, the PMMA/borax-treated devices exhibited significantly improved efficiency from 20.93% to 22.05% and retained 80% of the initial device performance over 1084 h at 22 degrees C and 50% RH. We believe that this technology will be useful for commercializing various optoelectronic devices.