Enhanced performance of inverted non-fullerene organic solar cells through modifying zinc oxide surface with self-assembled monolayers

Non-fullerene organic solar cells (OSCs) have attracted great attention due to their advantages such as tunable energy levels, reduced energy loss, strong light absorption. Here, three small molecules with polar functional groups were utilized to modify the surface of zinc oxide (ZnO) electron transport layer through self-assembled monolayers (SAMs) formation. Inverted non-fullerene OSCs with PBDB-T:ITIC blend as active layer based on the ZnO with SAMs modification showed enhanced device performance (10.90%) compared to that without SAM treatment (10.03%). The ultraviolet photoelectron spectroscopy results revealed that the SAMs could lower the surface work function of ZnO, allowing for better electron extraction. The analysis results of J-V characteristics under different light illumination intensities suggested more efficient charge dissociation and weaker trap-assisted bimolecular recombination in the devices with SAMs modification. Our work provides an effective approach to modify the ZnO surface for efficient non-fullerene OSCs.