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

Defectpassivation plays a critical role in manufacturing high-performanceperovskite solar cells (PSCs). Herein, engineered components of metforminhalides are introduced to the bulk and surface of perovskite layersin PSCs to realize synergistic defect passivation. It is found thatthe bulk addition of metformin hydrochloride influences the orientationdistribution of perovskite crystals and contributes to better perovskitefilms. Further, the modification of metformin iodide could treat residualdefects on the surface of perovskite films. As a result, the synergisticallypassivated PSCs shows an improved power conversion efficiency (PCE),which increased from 19.36% to 22.17%, together with a higher short-circuitcurrent and open-circuit voltage than those of the control device.Moreover, the as-treated PSCs exhibit excellent thermal and humiditystabilities, maintaining 95% of their initial PCE after being storedunder air conditions for over 1000 h. This work provides a novel strategyto passivate perovskite defects and improve the PCE and stabilityof PSCs.