Ultra-flexible organic solar cells based on eco-friendly cellulose substrate with efficiency approaching 19%

Flexible organic solar cells (OSCs), especially ultra-flexible OSCs, show great potential for applications in wearable devices and related fields. However, improving their performance remains a significant challenge in the flexible OSC field. Despite its importance as a key component in flexible devices, the flexible substrate has received relatively little attention, which indeed hinders further improvement in flexible OSC performance. In this study, we developed an eco-friendly, ultra-flexible substrate with high solvent resistance, outstanding mechanical durability, and excellent light transmittance by constructing an ethoxylated trimethylolpropane triacrylate (ETPTA) polymer network within an ethyl cellulose (EC) film. OSCs fabricated on this substrate achieved a record power conversion efficiency (PCE) of 18.71% and a high power-per-weight ratio of 30.04 W g-1. Furthermore, the ultra-flexible OSCs demonstrated excellent mechanical resilience, retaining 93.47% of their initial efficiency after 10 000 bending cycles at a bending radius of 1 mm.