Oligomeric Acceptor Enables High-Performance and Robust All-Polymer Solar Cells with 17.4% Efficiency

Developing efficient and stable all-polymer solar cells (all-PSCs) has received increasing attention because of their mechanical robustness for flexible devices. Based on the CH-series small molecule acceptors, a new polymer acceptor (PZC24) is reported and obtains a decent power conversion efficiency (PCE) of 16.82% when blended with PM6. To further improve the performance, an oligomeric acceptor (CH-D1), which possesses the same backbone structure as PZC24, is proposed and synthesized as the third component for all-PSC system. The creative strategy improves the crystallinity and molecular packing, and can maintain the efficient charge transport channels of the all-PSCs binary system. Therefore, the PM6:PZC24:CH-D1 based ternary devices exhibit an impressive PCE of 17.40%, among the highest value of all-PSCs. Compared to the PM6:PZC24, the ternary device exhibits enhanced photosoaking stability and thermal stability, simultaneously. In addition, the introduction of oligomeric acceptor does not weaken the mechanical robustness of all-PSCs. As such, the ternary flexible devices display an excellent PCE of 15.35%. Importantly, this strategy shows excellent universality in PM6:PY-IT and PM6:PY-V-gamma all-PSCs with improved PCEs over 17%. The results provide a feasible strategy to simultaneously improve photovoltaic efficiency and stability of all-PSCs devices and herald a bright future for all-PSCs.