Dual-Action Synergistic Enhancement of Photothermoelectric Properties of Flexible PEDOT:PSS/Cs x WO3 Composite Films

Abstract Photothermoelectric (PTE) devices with wide spectral response characteristics provide an effective way to capture low-grade solar energy and have broad application prospects in the field of flexible microenergy collection. Poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) has become a competitive candidate material for flexible PTE functional layers due to its excellent solution processing, mechanical flexibility, and electrical stability. However, the low photoelectric conversion efficiency of PEDOT:PSS limits its further application. In this work, PEDOT:PSS/CsxWO3 composite films combining excellent flexibility and photothermoelectric performance were fabricated via vacuum-assisted filtration. The increase in surface roughness induced by CsxWO3 nanoparticles and the Mie scattering effect significantly enhance the broadband light absorption of the film in the UV-Vis-NIR bands. At the same time, the energy barrier formed at the organic–inorganic interface triggers an energy filtering effect, optimizing the carrier transport properties. The PEDOT:PSS/CsxWO3 composite film with a CsxWO3 loading of 3 wt.% achieved a Seebeck coefficient of 25.56 μV K–1 and a power factor of 42.28 μW m–1 K–2, representing an approximately 2-fold enhancement compared to the pure PEDOT:PSS film. Furthermore, the 3 wt.% CsxWO3 composite film exhibited significantly enhanced photovoltage responses under multiwavelength laser irradiation and maintained stable voltage output after repeated bending and stretching cycles.