The Performance Comparison Between Fullerene and Nonfullerene Interlayers in Inverted Organic Solar Cells

Inverted fullerene organic solar cells with cathode modifying layers (CML) of ZnO/electron acceptor/polyethylenimine ethoxylated (PEIE) are fabricated, where electron acceptor is either [6,6]-phenyl C-71-butyric acid methyl ester (PC71BM) or a nonfullerene acceptor (IDIC). Compared to the devices based on conventional ZnO and ZnO/PEIE, the ones based on ZnO/PC71BM/PEIE and ZnO/IDIC/PEIE show increased short-circuit current densities (J(SC)), demonstrating both PC71BM and IDIC interlayers enhance the exciton splitting in donor phase located at the bottom of photoactive layer. The nearly same values ofJ(SC)based on ZnO/PC71BM/PEIE and ZnO/IDIC/PEIE imply the PC71BM and IDIC interlayers have almost identical capabilities of splitting excitons in donor phase, governed by the quadrupolarities and stacking modes of electron acceptors. The PC71BM and IDIC interlayers passivate the oxygen-deficient defects of ZnO surface, leading to the increases in fill factor (FF) of device; the ZnO/IDIC/PEIE gives larger FF than the ZnO/PC71BM/PEIE, indicating IDIC passivate ZnO more effectively than PC71BM. The current research provides some helpful insights into developing high-performance electron acceptors.