Biomimetic Electrodes for Flexible Organic Solar Cells with Efficiencies over 16%

Flexible organic solar cells (OSCs) are very promising for use in portable power supply devices due to the advantages of low-cost, light-weight, and flexibility. However, the efficiencies of flexible OSCs are limited by the flexible transparent electrodes owing to their nonoptimal electrical, optical, and mechanical properties. To address these challenges, leaf-like biomimetic electrodes are proposed to achieve an efficient light capture and glossy surface for a high-efficiency flexible OSC. To mimic the internal anatomy of the leaf, the conformable electrode stack consists of a flexible polyimide substrate, light-scattering polystyrene spheres, zinc oxide protecting layer, and electrically conductive silver nanowires to obtain a high transmittance, low sheet resistance, and low surface roughness. A record-high power conversion efficiency of 16.1% is realized by a flexible OSC with the biomimetic electrode design, comparable to those rigid devices on glass. Moreover, the flexible OSC on this biomimetic electrode exhibits a robust bendability against flexural strain, retaining 85% of the initial efficiency after 5000 bending cycles at a radius of curvature as small as 1.0 mm.