Realizing record efficiencies for ultra-thin organic photovoltaics through step-by-step optimizations of silver nanowire transparent electrodes

Ultra-thin (also known as ultra-flexible) organic photovoltaics (OPVs) represent a strong contender among emerging photovoltaic technologies. However, due to the imbalance between the optical and electrical properties of indium tin oxide (ITO)-free transparent electrodes, the ultra-thin OPVs often exhibit lower efficiency compared to the brittle yet more balanced rigid ITO counterparts. Here, we design and fabricate an advanced ultra-thin OPV, which involves a thoroughly optimized silver nanowires (AgNWs) transparent electrode (named AZAT) with excellent optical, electrical and mechanical properties. Specifically, the high-kinetic energy spray-coating method successfully yields a curve-shaped, tightly connected and uniformly distributed AgNWs film, complemented by a capping layer of zinc oxide:aluminum-doped zinc oxide (ZnO:AZO) to improve charge collection capability. Simultaneously, the transparency of the electrode is enhanced through precise optical optimization. Thus, we implant the AZAT-based devices on 1.3 μm polyimide substrates and demonstrate ultra-thin OPVs with a record efficiency of 18.46% and a power density of 40.31 W g⁻¹, which is the highest value for PV technologies. Encouragingly, the AZAT electrode also enables the 10.0 cm² device to exhibit a high efficiency of 15.67%. These results provide valuable insights for the development of ultra-thin OPVs with high efficiency, low cost, superior flexibility, and up-scaling capacity.