Solution-Processable All-Small-Molecules for High-Performance Nonfullerene Organic Solar Cells with High Crystallinity Acceptor

In this work, two small molecule acceptors (IDIC and IDIC-4F) with different crystallinities and energy levels have been successfully applied in nonfullerene-based all-small molecule organic solar cells (NFASM-OSCs). The donor DFDT(DPP)(2) was chosen because of complementary absorption with IDIC and IDIC-4F. As an acceptor, IDIC-4F exhibited a higher power conversion efficiency (PCE) than IDIC due to better crystallinity. This work not only shows us how to balance the relationship between V-oc and J(sc) but also suggests how to get a good phase separation morphology. Moreover, increased crystallinity helps to inhibit bimolecular recombination and increase charge mobility. By optimizing the device preparation conditions, the best PCE of 9.43% for DFDT(DPP)(2):IDIC-4F as an active layer was achieved with excitable J(sc) (16.83 mA cm(-2)) and fill factor (FF) (0.65). The FF and J(sc) of the resultant device show a significant increase, which is among the top efficiencies based on diketopyrrolopyrrole (DPP) being the terminal acceptor groups of NFSM-OSCs reported in the literature up to now.