An end-capped strategy for crystalline polymer donor to improve the photovoltaic performance of non-fullerene solar cells

Multi-component Copolymerized Donors enable Frozen Nano-morphology and Superior Ductility for Efficient Binary Organic Solar Cells

Multi-component copolymerized donors (MCDs) have gained significant interest and have been rapidly developed in flexible organic solar cells (f-OSCs) in recent years. However, ensuring the power conversion efficiency (PCE) of f-OSCs while retaining ideal mechanical properties remains an enormous challenge. The fracture strain (FS) value of typical high-efficiency blend films is generally less than 8 %, which is far from the application standards of wearable photovoltaic devices. Therefore, we developed a series of novel MCDs after meticulous molecular design. Among them, the consistent MCD backbone and end-capped functional group formed a highly conjugated molecular plane, and the solubilization and mechanical properties were effectively optimized by modifying the proportion of solubilized alkyl chains. Consequently, due to the formation of entangled structures with a frozen blend film morphology considerably improved the high ductility of the active layer, P10.8/P20.2-TCl exhibited efficient PCE in rigid (18.53 %) and flexible (17.03 %) OSCs, along with excellent FS values (16.59 %) in pristine films, meanwhile, the outstanding FS values of 25.18 % and 12.3 % were achieved by P10.6/P20.4-TCl -based pristine and blend films, respectively, which were one of the highest records achieved by end-capped MCD-based binary OSCs, demonstrating promising application to synchronize the realization of high-efficiency and mechanically ductile flexible OSCs.

All-Polymer Solar Cells with 17% Efficiency Enabled by the "End-Capped" Ternary Strategy

Recently, all-polymer solar cells (all-PSCs) have received increasing attention and made tremendous progress. However, the power conversion efficiency (PCE) of all-PSCs still lags behind the polymer-donor-small-molecule-acceptor based organic solar cells, owing to the excessive phase separation with poor miscibility between polymer donor and acceptor. In this research, an "end-capped" ternary strategy is proposed by introducing PM6TPO as a third component to fabricate highly efficient all-PSCs. The PM6:PM6TPO:PY-IT based ternary devices exhibit impressive PCE of 17.0% with enhanced light absorption and optimal morphology, and the introduction of PM6TPO significantly reduces the phase separation. The ternary devices also exhibit improved stability, outstanding tolerance of active layer thickness, and high performance of 1 cm² unit cells. More importantly, the "end-capped" ternary strategy enables efficient and facile improvement of all-PSCs performance without additional selection and complicated synthesis for the third component.