An intrinsically stretchable and bendable electrochromic device

Stretchable electrochromic devices were fabricated from electrospun PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrene sulfonate) fibers. Stretchable and transparent electrodes with a sheet resistance of 1200 Ω/sq were prepared by depositing the conductive fibers on elastomeric substrates that were prepared from polydimethylsiloxane. The conductive substrates replaced the ITO coated glass electrodes that are typically used in electrochromic devices. The functioning device was prepared from a flexible chitosan electrolytic gel and a 4,7-bis(4-diphenylaminophenyl)-2,1,3-benzothiaziazole (TPA-BZT-TPA) electrochrome that were deposited on the streatchable transparent electrodes. The assembled device could be stretched to 150% its original length and bent to a curvature of 0.1. The device could be operated and switched between its yellow (off) and blue (on) states while being stretched and bent with a maximum contrast ΔT ≈30% at 805 nm and a coloration efficiency of 168 cm2/C. The stretchable device had an electrochromic contrast that was 30% greater than its counterpart that was prepared from conventional ITO-glass electrodes. The critical composition required for making devices truly stretchable was possible by evaluating the performance of five types of devices consisting of different layers.