Impact of Symmetry-Breaking of Non-Fullerene Acceptors for Efficient and Stable Organic Solar Cells

Abstract

Here we report efficient and stable organic solar cells (OSCs) based on the asymmetric non-fullerene acceptor (NFA) IPC-BEH-IC2F. The NFA consists of the weak electron-donor core dithienothiophen[3.2-b]-pyrrolobenzothiadiazole (BEH) and two strong electron-acceptor (A) units [9H-indeno[1,2-b]pyrazine-2,3-dicarbonitrile (IPC) and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC2F)]. For comparison, the symmetric IPC-BEH-IPC and IC2F-BEH-IC2F were also characterized. Photovoltaic devices based on p-type polymer:NFA blends with PBDB-T and PM6 polymers were fabricated. PBDB-T:IPC-BEH-IC2F device displayed the best photovoltaic properties because the IPC unit provides balanced electronic and morphological characteristics. Importantly, the PBDB-T:IPC-BEH-IC2F device exhibited the best long-term stability owing to the strongly interacting IPC moiety and the densely packed PBDB-T:IPC-BEH-IC2F film.