Mechanically flexible multi-stacked ITO/PEDOT:PSS hybrid superlattice films for transparent conductive electrodes

Abstract

To improve the flexibility of transparent conductive electrodes (TCEs), we designed multi-stacked ITO/PEDOT:PSS hybrid superlattice (IxPy) films for flexible polymer-dispersed liquid crystal (PDLC), foldable thin-film heaters (TFHs), and flexible perovskite solar cells (PSCs). The electrical and optical properties of the multi-stacked IxPy films were examined and then optimized at the I6P5 film (ITO: 6 layers and PEDOT: 5 layers). The I6P5 film showed a sheet resistance of 149.66 Ohm/square, high transmittance of 93.75% at the visible range of (400–800) nm, and achieved the highest figure-of-merit (FOM) value of 3.50 × 10−3, compared with the other stacked conditions. Furthermore, the I6P5 films showed better flexibility by suppressing the brittle nature of ITO through inserting very thin PEDOT:PSS. The I6P5 film as an electrode was employed as a flexible PDLC, flexible TFHs, and flexible PSCs. The I6P5-based PDLC showed a clear distinction between on-state and off-state. At the applied voltage of 60 V, the transmittance of PDLC increased to 48.829% because of the arrangement of liquid crystals in the current direction. The flexible TFHs with I6P5 superlattice electrode showed high saturation temperature of above 100 °C at 14 V. Moreover, the I6P5 electrodes showed similar efficiency to reference ITO films in flexible PSCs. These results indicate that the multi-stacked IxPy hybrid superlattice films offer superior potential as highly transparent and foldable or flexible conductive electrodes.