The mechanism of conductivity enhancement in poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic) acid using linear-diol additives: Its effect on electrochromic performance

The conductivity of poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic) acid (PEDOT–PSS) thin-films was increased by up to 900 times with the addition of linear-diols. Three series of linear-diols were investigated. It is proposed that three mechanisms contribute to improved conductivity; conformational changes in the polymer from coil to expanded, spatial separation of PEDOT–PSS grains and charge screening. The variation in conductivity with temperature indicates that diols affect both intra- and inter-chain charge transports. Electrochromic devices were constructed using standard and enhanced conductivity PEDOT–PSS. Switching times from bleached to darkened states were reduced while darkened to bleached states remained unaltered. Total percent transmission change (%ΔTx) remained constant indicating that enhanced conductivity PEDOT–PSS improves switching but does not lead to additional electrochromic redox sites being accessed.