Application of NADH- modified ZnO electron transport layer in high performance organic solar cells

Abstract

As an electron transport layer (ETL) widely used in organic solar cells (OSCs), ZnO has problems of energy level mismatch with the active layer and excessive defects on the ZnO surface, which ultimately reduce the efficiency of OSCs. Here, the ZnO:NADH ETL is prepared by modifying the ZnO with green biomaterial nicotinamide adenine dinucleotide (NADH). XPS and UPS show that ZnO obtains electrons from NADH and decreases work function of ZnO, thus lowering the interface barrier between ZnO and active layer, which is conducive to electron collection in OSCs. At the same time, the oxygen vacancy density on the ZnO surface reduces after modification with biomaterial NADH, thus improving the electrical conductivity of ZnO. Finally, we use PM6:Y6 and PM6: L8-BO as active layers, and use ZnO:NADH as a novel ETL in OSCs, achieving efficiencies of 16.77% and 18.21%, respectively. The stability of the device with ZnO:NADH ETL has also been improved to a certain extent. This study provides an effective method for ZnO modification, and also contributes to the environmental protection in the device preparation process.