Highly efficient fiber-shaped organic solar cells toward wearable flexible electronics

Fiber-shaped organic solar cells (FOSCs) are promising power sources for wearable electronics due to their all-solid-state nature, ease of fabrication, environmental friendliness, and material stability. However, their efficiency has lagged behind other fiber-shaped solar cells. This work introduces non-fullerene acceptor (NFA)-based photoactive materials into FOSCs and employs low-cost industrial stainless-steel wire as the core electrode, with carbon nanotube yarn or silver wire as the counter electrode. Using a solution-processed PDINO electron transport layer and a PM6:Y6:PC71BM ternary active layer, FOSCs achieve up to 9.40% power conversion efficiency under AM 1.5 G. Systematic studies of transport layers, active layer, counter electrodes, solvents, and especially environmental humidity reveal key performance determinants. The devices can drive small electronics, be woven into textiles, and charge a smartwatch, highlighting strong potential for wearable applications.