Flexible ITO-Free Organic Solar Cells Based on Anodes

Flexible organic solar cells (OSCs) using our proposed MoO₃ (2 nm)/Ag (9 nm) anode are fabricated on poly(ethylene terephthalate) (PET) substrates with poly(3hexylthiophene) (P3HT) and [6,6]-phenyl-C61 -butyric acid methyl ester (PCBM) films as the active layer. Power conversion efficiency (PCE) of 2.50% is achieved for such flexible indium tin oxide (ITO)-free OSCs under 1 sun AM 1.5G simulated illumination, which is comparable with that of the same devices fabricated on glass substrates (PCE of 2.71%) or that of ITO-based reference OSCs on glass (PCE of 2.85%). Meanwhile, such flexible ITO-free OSCs show good mechanical flexibility. A 10% degradation in PCE is observed after 500 inner bending cycles with a bending radius of 1.5 cm, whereas a 5% decrease in PCE is observed after 500 outer bending cycles. Furthermore, the flexibility of the structure PET/MoO₃/Ag/MoO₃ has been investigated. Its transparency almost remains constant, and its sheet resistance varies negligibly after 1000 cycles of inner or outer bending tests. It shows the huge potential of our flexible electrodes, and it may be instructive for further research on flexible electrodes.