Multifunctional Iron–Porphyrin Additive for Hole‐Transporting Layer Toward Efficient and Stable Perovskite Solar Cells

Abstract

Spiro‐OMeTAD, as a crucial component of hole‐transporting layer (HTL), exhibits limited mobility and conductivity, and the lithium bis‐trifluoromethanesulfonimide dopant is sensitive to water vapor, which imposes restrictions on the photovoltaic properties of perovskite solar cells (PSCs). Herein, the iron–porphyrin (FePP) is introduced into Spiro‐OMeTAD solution as additive, which facilitates the oxidation process of Spiro‐OMeTAD, leading to the enhancement of hole mobility and hole extraction and transport. Besides, the surface Pb2+ defects of perovskite film are cured by the presence of carboxylic acids (COOH) in FePP. As a result, the photovoltaic properties of PSCs with FePP additive have been improved with a power conversion efficiency (PCE) of 21.58%. Moreover, FePP can further anchor Li+ ions in HTL to prevent it from being invaded by water vapor. Dramatically, the degradation of unencapsulated devices with FePP is suppressed significantly, which retains 82.0% of its original PCE under 10–20% relative humidity (RH) after 7100 h and maintains about 79.6% of its original PCE under 50–60% RH after 1000 h. Thus, this study shows that the design and development of multifunctional HTL additives holds great potential for achieving highly efficient and durable PSCs.