Synergistic Defect Passivation by Metformin Halides for Improving Perovskite Solar Cell Performance

Abstract

Defect passivation plays a critical role in manufacturing high-performance perovskite solar cells (PSCs). Herein, engineered components of metformin halides are introduced to the bulk and surface of perovskite layers in PSCs to realize synergistic defect passivation. It is found that the bulk addition of metformin hydrochloride influences the orientation distribution of perovskite crystals and contributes to better perovskite films. Further, the modification of metformin iodide could treat residual defects on the surface of perovskite films. As a result, the synergistically passivated PSCs shows an improved power conversion efficiency (PCE), which increased from 19.36% to 22.17%, together with a higher short-circuit current and open-circuit voltage than those of the control device. Moreover, the as-treated PSCs exhibit excellent thermal and humidity stabilities, maintaining 95% of their initial PCE after being stored under air conditions for over 1000 h. This work provides a novel strategy to passivate perovskite defects and improve the PCE and stability of PSCs.