A passivation–reduction synergistic strategy for achieving efficient and durable inverted perovskite solar cells

Abstract

The presence of iodine vacancy defects and iodine impurities on the surface of perovskite can greatly limit the efficiency and stability of perovskite solar cells (PSCs). Therefore, it is crucial to develop a surface iodine management strategy that can passivate surface defects and eliminate harmful I₂. This work reports the use of sodium triacetoxyborohydride (STAB) as a reductive anionic passivator for post-treatment of the perovskite surface. The study shows that the multiple electron-rich carbonyl groups of STAB can multidentately coordinate with undercoordinated Pb²⁺ and suppress iodine vacancy defects. Meanwhile, the reductive nature of STAB prevents the conversion of I⁻ to I₂. This alleviates surface iodine loss, reduces the byproduct Pb⁰, and effectively mitigates the decomposition of perovskite films. Through this synergistic surface iodine management strategy of passivation and reduction, STAB-treated PSCs achieved a power conversion efficiency (PCE) of 25.85%. After 1000 hours of maximum power point tracking at 65 °C, they still retained more than 90% of their initial efficiency. When STAB was applied to narrow-bandgap 1.27 eV perovskite, the PCE increased from 20.02% to 22.97%, demonstrating the universality of this method for different bandgap perovskite systems.