SnS/PEDOT:PSS composite films with enhanced surface conductivities induced by solution post-treatment and their application in flexible thermoelectric

Developing low-cost and high-performance thermoelectric materials is warranted. Herein, a series of flexible thermoelectric organic–inorganic composite films of tin sulfide (SnS)/poly(3, 4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and SnS/PEDOT:PSS/multiwalled carbon nanotube (MWCNT) are prepared by drop coating. Then, a water–methanol solution is spun on the composite films to further improve the upper surface layer's conductivity. This facile water–methanol post-treatment does not affect the lower part of the film, which keeps the Seebeck coefficient of the film from being significantly reduced. As a consequence, SnS/PEDOT:PSS films show the most significant conductivity increase rate of 28.8% and the maximum power factor (PF) of 43.11 μW m−1 K−2, whereas those for the SnS/PEDOT:PSS/MWCNT films are 4.5% and 44.54 μW m−1 K−2, respectively. In addition, the prepared composite films show good stability in bending tests and could be applied to construct six-legged flexible thermoelectric devices to evaluate the prospects of the flexible thermoelectric application of these films. Our strategy for film design offers a new idea for thermoelectric research.