Brändler, LisaLisaBrändlerNiklaus, LukasLukasNiklausLöbmann, PeerPeerLöbmannSchott, MarcoMarcoSchottGiffin, GuinevereGuinevereGiffin2025-06-262025-06-262025https://publica.fraunhofer.de/handle/publica/48898010.1002/admt.202500236The thermal stability of polymeric electrochromic devices (ECDs) on flexible substrates is crucial for most applications. In this study, the high-temperature cycling stability of the side-chain modified poly(3,4-ethylenedioxythiophene) (PEDOT-EthC6) and Prussian blue (PB) ECDs on indium tin oxide coated polyethylene terephthalate (PET-ITO) is investigated up to 60 °C. Without a temperature-dependent voltage control, a loss of optical contrast of 21% over 10 000 cycles at 60 °C and ±1.1 V is observed. Analysis of the cycled ECDs and cyclic voltammetry of the electrodes reveal that side reactions of the EC materials occur during cycling. A local aggregation state of the PEDOT-EthC6 is degraded. The PB electrode is overoxidized toward Prussian green as confirmed by UV-vis spectroscopy. Raman spectroscopy shows an altered doping state of the PEDOT-EthC6 electrode after cyclic voltammetry measurements up to 80 °C. The temperature-dependent onset potentials of the side reactions are determined. By cyclic voltammetry of ECDs with a Li reference electrode, safe voltage windows are established. With −0.55 V / +1.1 V, 91% of the initial contrast of τv = 10% ↔ 65% is retained over 10 000 cycles at 60 °C. The results demonstrate that an adaptation of switching parameters for temperature can improve the thermal stability of polymeric ECDs.encyclic voltammetryelectrochromic devicesPEDOTPrussian bluetemperature stabilitythree-electrode cells500 Naturwissenschaften und Mathematik::530 Physik500 Naturwissenschaften und Mathematik::540 Chemiejournal article