Diaminobenzene Dihydroiodide‐MA0.6FA0.4PbI3−xClx Unsymmetrical Perovskites with over 22% Efficiency for High Stability Solar Cells

Abstract 2D perovskites exhibit limited charge transfer and a stable unsymmetrical structure. Hence, a 2D perovskite solar cell (PSC) is more stable but less efficient than a 3D PSC. An effective combination of good stability and high power conversion efficiency (PCE) is desirable in PSCs. A novel diaminobenzene dihydroiodide‐MA 0.6 FA 0.4 PbI 3− x Cl x analogous 2D unsymmetrical perovskite is designed to further enhance PSC performance. The two amino groups of diaminobenzene dihydroiodide (DD) function similarly as the amino groups of methylammonium and formamidinium ions. Therefore, diaminobenzene dihydroiodide can replace methylammonium and formamidinium and create better bonding interaction with the lead trihalide. The analogous 2D unsymmetrical perovskite not only possesses sufficient charge transfer but also exhibits high stability with an appropriate incorporation of DD. Noticeably, the champion device shows a PCE of 22.34%, setting a new record for an MAPbI 3− x Cl x based PSC. The thermal, illumination, and environmental stability is enhanced by 20%–30%. The improved PCE and stability is attributed to better charge transfer and stable structure.