?-Extension and chlorination of non-fullerene acceptors enable more readily processable and sustainable high-performance organic solar cells

Organic solar cells (OSCs) processed without halogenated solvents and complex treatments are essential for future commercialization. Herein, we report three novel small molecule acceptors (NFAs) consisting of a Y6-like core but with 7C-extended naphthalene with progressively more chlorinated end-capping groups and a longer branched chain on the Nitrogen atom. These NFAs exhibit good solubilities in non -chlorinated organic solvents, broad optical absorptions, close 7C -7C stacking distances (3.63-3.84 angstrom), and high electron mobilities (-10-3 cm2 V-1 s-1). The o-xylene processed and as-cast binary devices using PM6 as the donor polymer exhibit a PCE increasing upon progressive chlorination of the naphthalene end-capping group from 8.93% for YN to 14.38% for YN-Cl to 15.00% for YN-2Cl. Furthermore similarly processed ternary OSCs were fabricated by employing YN-Cl and YN-2Cl as the third component of PM6:CH1007 blends (PCE = 15.75%). Compared to all binary devices, the ternary PM6:CH1007:YN-Cl (1:1:0.2) and PM6:CH1007:YN-2Cl (1:1:0.2) cells exhibit significantly improved PCEs of 16.49% and 15.88%, respectively, which are among the highest values reported to date for non-halogenated solvent processed OSCs without using any additives and blend post-deposition treatments.(c) 2022 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by ELSEVIER B.V. and Science Press. All rights reserved.

Automated summary

In this study, three novel small molecule acceptors were developed, which showed good solubilities in non-chlorinated organic solvents, broad optical absorptions, close molecular stacking distances, and high electron mobilities. The solar cells fabricated using these acceptors achieved high power conversion efficiencies without halogenated solvents or additives.