Balanced shelf and operational stability of the PM6:Y6 solar cells by using ZnO:PEI composite electron transporting layer

The operational stability under continuous illumination and the shelf stability in air are all important for the real application of the organic solar cells (OSCs). In this work, we investigated the influence of the commonly used electron transporting layer (ETL), i. e. ZnO and polyethyleneimine (PEI) on the shelf and operational stability of the PM6:Y6 OSCs. Due to the photocatalysis effect of ZnO, the operational stability of ZnO ETL-based device is worse than the PEI ETL-based device. Due to the hygroscopicity of PEI, the shelf stability of the PEI ETL-based device is worse than the ZnO ETL-based device. By using a ZnO:PEI composite ETL, a balanced shelf and operational stability was obtained. For the inverted PM6: Y6 solar cells, the device could remain 80% and 60% of the initial efficiency after 1200 h continuous illumination, and storage in air for 1500 h, respectively.