Black-to-Transmissive Electrochromic Switching PEDOT-co-poly(N-ethylcarbazole) via a Sustainable and Facile In Situ Photo(co)polymerization Method

It is a great challenge to obtain black-to-transmissive switches using one type of polymer. Therefore, the color blending/mixing theory has been previously applied by many research groups to produce black-to-transmissive materials (BTMs) through the (electro)chemical copolymerization of several monomers. However, these (electro)chemical copolymerization methods exhibited numerous drawbacks in terms of sustainability. In this work, for the first time, the synthesis of an electrically conductive (bromide-doped) poly(3,4-ethylenedioxythiophene)-poly(N-ethylcarbazole) (PEDOT-co-PECz) copolymer was demonstrated using an in situ and sustainable photopolymerization technique. Spectrally and microscopically characterized copolymers were then deposited onto ITO/glass using spray coating. The copolymer film demonstrated to switch from a black state (L*: 38.16; a: −0.33; b: −2.89) to a transmissive state (L* = 83, a* = −3, b* = −6) with a contrast of 31.6% ΔT at 650 nm in fast response times (2.28–4.38 s). The results highlight the importance of this advanced method for the sustainable and fast fabrication of smart windows.