Molecular Design of Self-Doping Cathode Interlayer for Efficient and Humidity-Resistant Organic Photovoltaic Cells
Yue Yu, Yong Cui, Zhihao Chen, Miaoning Ou, Tao Zhang, Yang Xiao, Di Jia, Zhen Fu, Guanlin Wang, Junzhen Ren, Xiaotao Hao, Jianhui Hou
Abstract
The power conversion efficiency (PCE) of organic photovoltaic (OPV) cells has surpassed 20%. However, their stability remains a critical issue that requires further improvement, particularly due to severe performance degradation under humid conditions. To tackle this challenge, a series of cathode interlayer materials─NDIP-M, NDIP3F-M, and NDIP4F-M─were rationally designed and synthesized through side-chain engineering combined with fluorination strategies. These materials exhibit enhanced hydrophobicity and maintain good solubility in alcohol-based solvents. Among them, NDIP3F-M showed optimized energy level alignment and reduced trap activation energy, leading to an improved fill factor and a PCE of 20.1%. Notably, due to the excellent humidity resistance of NDIP3F-M, an unencapsulated OPV cell based on NDIP3F-M retained 50% of its initial PCE after 400 h of exposure to air at 85% relative humidity, which is significantly higher than that of OPV cells employing commonly used cathode interlayer materials.