Vitamin C-Induced Enhanced Performance of PEDOT:PSS Thin Films for Eco-Friendly Transient Thermoelectrics

Conjugated polymer-based energy-harvesting devices hold distinctive advantages in terms of low toxicity, high flexibility, and capability of large-area integration at low cost for sustainable development. An organic thermoelectric (OTE) device has been considered one of the promising energy-harvesting candidates in recent years because it can efficiently convert low-temperature waste heat into electricity over its inorganic counterparts. However, a cruel irony is that environmentally toxic solvents and acids are utilized for fabrication and performance improvement of the OTE devices, retarding the development and use of genuinely green energy-harvesting. Here, we present eco-friendly, non-toxic strategies for a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based high-performance OTE device by incorporating a nature-abundant material, vitamin C (VC), as an additive. We found that the intrinsic polar nature and reducing ability of VC induce synergy effects of microstructure alignment with PSS removal and dedoping of PEDOT, leading to simultaneous enhancement of the electrical conductivity (>400 S cm^-1) and the Seebeck coefficient (>30 μV K^-1) and a resultant high thermoelectric power factor of 51.8 μW m^-1 K^-2. In addition, inspired by the eco-friendly fabrication process, we further demonstrated a transient OTE device, which can be fully degraded with naturally occurring substances, by fabricating it on a bio-based cellulose acetate substrate. We believe that our eco-friendly strategies from fabrication to disposal of the OTE can be applied to the development of high-performance, wearable, and bio-compatible OTE devices with minimal waste and further trigger the research on genuinely green thermal energy harvesting.