Bifunctional Chlorosilane Modification for Defect Passivation and Stability Enhancement of High-Efficiency Perovskite Solar Cells

Improving the photoelectric conversion efficiency and long-term stability are two substantial goals for the research work of perovskite photovoltaics, which can be realized through appropriate surface modification methods. In this work, we report a bifunctional modification strategy using (3-chloropropyl)trimethoxysilane with the aim to increase the efficiency and stability of the as-fabricated perovskite solar cells (PSCs) simultaneously. The mechanism of such bifunctional modification is studied with systematic spectroscopic and transient photoelectric characterizations. Specifically, the enhancement of efficiency results from the chlorine-induced passivation of iodine-vacancy trap states, as evidenced by the decrease of trap-state density through the interaction between chlorosilane and Pb2+, which further leads to the prolonged photoluminescence lifetime of the intrinsic perovskite films and suppressed charge recombination of photovoltaic devices. The corresponding champion device possesses a power conversion efficiency of 18.14%, 16% higher than that of the control device. In addition, the modified perovskite films exhibit superior moisture resistance owing to the introduced hydrophobic silane network, and the corresponding devices could preserve ∼85% of the initial efficiency after 2 months' storage under ambient air conditions. The proposed bifunctional modification strategy and the mechanism studies provide new insights into both efficiency and stability engineering of the PSCs.