An efficient alkoxy-substituted polymer acceptor for efficient all-polymer solar cells with low voltage loss and versatile photovoltaic applications

Abstract

All-polymer solar cells (all-PSCs) have emerged as promising candidates for practical applications owing to their excellent stability and mechanical durability. Despite these merits, the device performance of all-PSCs still falls behind those based on small-molecule acceptors. The critical challenge lies in balancing and enhancing both the open-circuit voltage (V_OC) and the short-circuit current density (J_SC) in a synergistic manner. Herein, we designed an acceptor, PYO-V, with upshifted energy levels as well as blue-shifted absorption by linking alkoxy side chains on the β position of the outer thiophene units. The introduction of PYO-V into the PM6:PY-V-γ host system complements its absorption spectrum, improving its molecular packing, suppressing its charge recombination, and enhancing its polaron generation efficiency. Consequently, the resulting ternary all-PSCs with 20 wt% PYO-V achieved a significantly enhanced efficiency of 18.5%, which represents the highest value for reported all-PSCs with a V_OC of over 0.93 V. Moreover, the hypsochromic PYO-V also displays its versatile applications in indoor photovoltaics, as the PYO-V-based binary device achieves an efficiency of over 24%, among the best performance for indoor all-PSCs. This work presents an effective strategy for designing polymer acceptors with wider bandgaps for outdoor and indoor photovoltaic applications.