Polymer‐Entangled Spontaneous Pseudo‐Planar Heterojunction for Constructing Efficient Flexible Organic Solar Cells

Abstract Flexible organic solar cells (FOSCs) have attracted considerable attention from researchers as promising portable power sources for wearable electronic devices. However, insufficient power conversion efficiency (PCE), intrinsic stretchability, and mechanical stability of FOSCs remain severe obstacles to their application. Herein, an entangled strategy is proposed for the synergistic optimization of PCE and mechanical properties of FOSCs through green sequential printing combined with polymer‐induced spontaneous gradient heterojunction phase separation morphology. Impressively, the toughened‐pseudo‐planar heterojunction (Toughened‐PPHJ) film exhibits excellent tensile properties with a crack onset strain (COS) of 11.0%, twice that of the reference bulk heterojunction (BHJ) film (5.5%), which is among the highest values reported for the state‐of‐the‐art polymer/small molecule‐based systems. Finite element simulation of stress distribution during film bending confirms that Toughened‐PPHJ film can release residual stress well. Therefore, this optimal device shows a high PCE (18.16%) with enhanced (short‐circuit current density) J_SC and suppressed energy loss, which is a significant improvement over the conventional BHJ device (16.99%). Finally, the 1 cm² flexible Toughened‐PPHJ device retains more than 92% of its initial PCE (13.3%) after 1000 bending cycles. This work provides a feasible guiding idea for future flexible portable power supplies.