Additive-Free, Efficient, and Stable All-Polymer Solar Cells Enabled by Congeneric Molecule Construction for...

Organic solar cells are attractive for wearable electronics, in particular, all-polymer solar cells (all-PSCs) offer superior intrinsic stability and higher output voltage, enabling direct matching with the energy storage and conversion systems. However, all-PSCs typically suffer from disordered morphology and poor donor-acceptor compatibility, requiring processing additives that compromise long-term stability. Here, we introduce a structural homology strategy, using donor and acceptor polymers that share the same bithiophene imide building block, to eliminate the need for additives. This design strengthens intermolecular interactions, enhances molecular ordering, and suppresses energy loss, yielding an open-circuit voltage of 0.94 V, a 12% improvement over the benchmark PM6:Y6 system. The chemical homology also reduces the Flory-Huggins interaction parameter and improves donor-acceptor compatibility, allowing the active layer to spontaneously form an ideal nanoscale fibrillar interpenetrating network. The resulting additive-free all-PSCs achieve a record power conversion efficiency of 19.12%, together with exceptional thermal stability (T₈₀  =  1128 h), photostability (T₈₀  = 756 h), and mechanical robustness. By integrating a 70 cm² large-area all-polymer module with series-connected zinc-air batteries, we demonstrate a self-sustaining, solar-rechargeable system that delivers continuous power under both illumination and darkness, offering a practical pathway for next-generation flexible and wearable electronics.