An Efficient and Stable Inverted Structure Organic Solar Cell Using ZnO Modified by 2D ZrSe2 as a Composite Electron Transport Layer

Abstract As an electron transport layer (ETL) widely used in organic solar cells (OSCs), ZnO has problems with energy level mismatch with the active layer and excessive defects on the ZnO surface, which can reduce the efficiency of OSCs. Here, ZnO/ZrSe 2 composite is fabricated by modifying ZnO with 2D ZrSe 2 . The XPS and first‐principles calculation (FPC) show that ZnO obtains electrons from ZrSe 2 and forms interfacial dipoles toward the active layer, which decreases the work function of ZnO, thus reducing the interface barrier and favoring the collection of electrons in OSCs. At the same time, after ZrSe 2 modification, the oxygen vacancy density on the ZnO surface decreases, thus improving the conductivity of ZnO. More importantly, the femtosecond transient absorption (Fs‐TA) shows that ZrSe 2 selectively traps holes from the active layer, which prevents the holes from entering the ZnO, thereby reducing the probability of electron recombination. Finally, ZnO/ZrSe 2 composite is used as a novel ETL in OSCs with PBDB‐T: ITIC, PM6:Y6 and PM6: L8‐BO as active layers, and obtaining 12.09%, 16.34%, and 18.24% efficiency, respectively. This study provides a method for the interface modification of ZnO, and further investigates the role of 2D nanosheets in the interface modification.