Highly Flexible All‐Polymer Solar Cells Processed without Post‐Treatment Achieving 13.56% Efficiency

The many merits of organic solar cells such as light weight, flexibility, and printability rely heavily on flexible devices. In this regard, all‐polymer solar cells (PSCs) are the primary choices due to the superior flexibility and mechanical properties of polymers over small molecule and fullerene materials. However, the polymer batch discrepancy and the multifarious post‐treatment steps are serious obstacles to practical applications. Herein, highly efficient and mechanically robust all‐PSCs based on a new polymer acceptor PYSe‐2FT and polymer donor D18 are developed. Without any post‐treatment, the flexible all‐PSC exhibits high power conversion efficiency (PCE) of 13.56%, which stands among the best values in flexible all‐PSCs so far. Bending tests reveal that the flexible device maintains 86% efficiency of the original PCE after 1000 bending cycles with a narrow curvature radius of 3 mm. More importantly, the all‐PSC efficiencies are insensitive to the molecular weight of the newly developed acceptor polymer, which possesses favorable universality and stability when working together with various donors. The superior mechanical properties and the ease of process make this all‐PSC a promising candidate for applications in flexible and portable devices.