N-Type Alcohol-Soluble Small Molecules as an Interfacial Layer for Efficient and Stable Polymer Solar Cells

Abstract

Three novel n-type alcohol-soluble small molecule electrolytes (n-SMEs) based on the diketopyrrolopyrrole (DPP) backbone functionalized with different polar groups (diethylamino, diethanolamino, quaternary ammonium), called DPPN, DPPNOH, and DPPNBr, respectively, have been designed and synthesized, respectively. Thanks to the chemical interaction with zinc oxide (ZnO), the n-SMEs can be easily deposited on the ZnO surface, and then we modified ZnO defects, fine-tuned the work function of ZnO, and simultaneously improved the compatibility at the ZnO/active layer inorganic/organic interface. Moreover, the n-type feature of the backbone in the n-SMEs also facilitates the electron transfer. Consequently, these n-SME-modified ZnO can serve as an efficient electron-transporting layer (ETL) in inverted polymer solar cells (I-PSCs). Inspiringly, the device based on poly(3-hexylthiophene) (P3HT):(6,6)-phenyl-C61 butyric acid methyl ester (PC61BM) with ZnO/DPPNOH as ETL delivers a notable power conversion efficienc...