Flexible, stripe-patterned organic solar cells and modules based on multilayer-printed Ag fibers for smart textile applications

Rapid advancement in the fabrication technologies of stripe/fiber-shaped optoelectronic devices has driven the performance of smart textile electronics to a new height. In the development of high-performance smart textile electronics, indium tin oxide (ITO)-free flexible transparent conductive electrodes (TCEs) are particularly desirable because they offer superior flexibility and lower manufacturing cost than the brittle ITO-based counterparts. Herein, we innovatively combine spin-coating and three-dimensional direct-ink writing (three-dimensional-DIW) techniques to develop large-area (5 × 5 cm²) PEDOT:PSS/Ag-fibers hybrid TCEs (denoted as DIW-TCEs) for application in flexible organic solar cells (OSCs). Through a multilayer printing strategy, high aspect-ratio Ag-fibers are successfully deposited on top of the planar PEDOT:PSS film. The resulting DIW-TCEs, when fully embedded in a colorless polyimide substrate, exhibit excellent electrical conductivity (sheet resistance ∼ 4 Ω/□), superior optical transmittance, and mechanical flexibility. One-dimensional stripe-patterned OSCs (stripe-OSCs) based on DIW-TCEs achieved power conversion efficiency of 9.3% and 8.2% at an active area of 0.11 cm² and 0.31 cm², respectively. For real-life application, a flexible power module was constructed using eight stripe-OSCs. When attached on textile, the module successfully lit up a commercial light-emitting diode upon photocharging. The unique DIW-TCE fabricated herein can be the ITO-free alternative for the production of smart textile electronics.