In situ Raman spectroscopy of thermal phase transformation of ET2I3 polycrystalline network in polymer films

Raman microscopy was used for studying the thermal transformation of α- to βt-phase of polycrystalline ET2I3 thin layers (ET=bis(ethylenodithio)tetrathiafulvalene) in polycarbonate film prepared by the two step reticulate doping technique (RDT). The in situ resonant Raman spectroscopy provides the unique possibility to observe the stretching frequency change of the I3− anion in ET2I3 salt during annealing. This potentially enables to find the optimum conditions for phase transformation. For the polycarbonate (PC)+α-ET2I3 system, 1-h annealing at 107±1°C was found to be optimal, as confirmed by the temperature dependence of the resistivity.