Ternary copolymer strategy enables solubility-mediated aggregation control for high-performance ternary all-polymer solar cells

Abstract

The ternary strategy has emerged as a pivotal approach for achieving high-performance organic solar cells (OSCs). Herein, we introduce a structurally compatible ternary polymer donor, PMz-5, into the PBQx-TF:PY-IT binary system to mitigate excessive aggregation of PBQx-TF. PMz-5 exhibit excellent miscibility with PBQx-TF in ternary films due to their similar building blocks. Systematic investigations reveal that PMz-5 forms an alloy-like structure with PBQx-TF, inducing a monotonic increase in open-circuit voltage (V_OC) in ternary devices. This synergistic interaction not only boosts addition charge transfer from PBQx-TF to PMz-5 through forming favorable energy level alignment but also suppresses the charge recombination by regulating the crystallite coherence length and phase-separation domain size in the photoactive layer. Consequently, the optimized ternary blend film exhibits refined morphology and enhanced charge dynamics, achieving a champion PCE of 17.15 % with a short-circuit current density (J_SC) to 24.33 mA cm⁻², a V_OC of 0.952 V, and a fill factor (FF) of 74.03 %. This work demonstrates that third component engineering with judiciously designed ternary polymers can simultaneously address morphological and electronic challenges in all-polymer solar cells (APSCs), offering a generalized framework for advancing multi-component OSCs through molecularly tailored strategy.