Manipulating Polymer Backbone Configuration via Halogenated Asymmetric End‐Groups Enables Over 18% Efficiency All‐Polymer Solar Cells

Abstract High‐performance all‐polymer solar cells (all‐PSCs) deeply rely on the joint contributions of desirable optical absorption, adaptive energy levels, and appropriate morphology. Herein, two structural analogous polymerized small‐molecule acceptors (PSMAs), PYFCl‐T and PYF&PYCl‐T, are synthesized, and then incorporated into the PM6:PY‐IT binary blends to construct ternary all‐PSCs. Due to the superior compatibility of PY‐IT and PYFCl‐T, the ternary all‐PSC based on PM6:PY‐IT:PYFCl‐T with 10 wt% PYFCl‐T, presents higher and more balanced charge mobility, suppressed charge recombination, and faster charge‐transfer kinetics, resulting in an outstanding power conversion efficiency (PCE) of 18.12% with enhanced J_sc and FF, which is much higher than that (PCE of 16.09%) of the binary all‐PSCs based on PM6:PY‐IT. Besides, the ternary all‐PSCs also exhibit improved photostability. The conspicuous performance enhancement principally should give the credit to the miscibility‐driven phase optimization of the donor and acceptor. These findings highlight the significance of polymer‐backbone configuration modulation of PSMAs in morphology optimization toward boosting the device properties of all‐PSCs.