Exceptional Electrochromic Solar Modulation Using Polyanionic Dopant Templated Poly(diphenylamine) Thin Films

We report poly(diphenylamine) thin films with exceptional optical clarity (Tvis ≥ 0.80) and electrochromic solar modulating ability (ΔTsol ≥ 0.60). Electropolymerizing diphenylamine in the presence of a polyanionic acid dopant is critical to achieving high macroscale uniformity and smoothness, which minimizes optical scattering and maximizes electrochromic response throughout the visible (>400 nm) and near-infrared (>700 nm) spectral ranges. We then use combinations of near- and far-field spectroscopies and their imaging modes to elucidate the roles of dopants in directing polymerization and resulting chain conformational order. By comparing small molecule and polymeric sulfonic acid dopants, we determine that the latter template poly(diphenylamine) polymerization to achieve superior morphological characteristics responsible for high electrochromic contrast. The results demonstrate the potential of these polymeric materials as active layers or components in smart window applications.