Vacuum vapour phase polymerised poly(3,4-ethyelendioxythiophene) thin films for use in large-scale electrochromic devices

Large-scale electrochromic devices were manufactured using vacuum vapour phase polymerised (VPP) poly(3,4-ethylenedioxythiophene) (PEDOT). Homogeneous 3,4-ethylenedioxythiophene (EDOT) and water vapour distribution within the large 115 L VPP chamber is paramount for the reproducible synthesis of high conductivity PEDOT thin films. Obtaining these conditions, however, was not trivial. The issue was resolved by synthesising PEDOT under vacuum, however, this altered the dynamics of the polymerisation process. As a result, surfactant addition, monomer and water vapour distribution, monomer and chamber temperature, and polymerisation times were all systematically investigated. Controlling these parameters has resulted in PEDOT with conductivity exceeding 1100 S · cm⁻¹, with a best of 1485 S · cm⁻¹, and electrochromic devices with an optical switch of Δ%Tx ≥ 50%. The resulting high conductivity and optical range are due to long undisrupted PEDOT polymer chains coupled with low levels of oligomers within the matrix.