Transparent flexible thin-film p-n junction thermoelectric module

Transparent and flexible thermoelectrics has been highly sought after for future wearable devices. However, the main stumbling block to prevent its widespread adoption is the lack of p-type transparent thermoelectrics and the stringent criteria of electrical and thermal properties matching appropriately between p-legs and n-legs. This work demonstrates the fabrication of p-type PEDOT:PSS films whose optical properties, electrical conductivity, thermal conductivity, and Seebeck coefficient were engineered to perfectly match the n-type indium tin oxide (ITO) counterparts. The dense p-type PEDOT:PSS and n-type ITO thin films show a thermoelectric figure of merit of zT=0.30 and 0.29 at 450K, and a thermal conductivity of 0.22 and 0.32Wm(-1)K(-1), respectively. A flexible thermoelectric generator (TEG) module with a high transmittance of >81% in the visible wavelength range of 400-800nm is fabricated using 10 pairs of p-type PEDOT:PSS and n-type ITO thin film legs. An ultra-high power density of 22.2Wm(-2) at a temperature gradient of 80K was observed, which is the highest power density reported for organic/hybrid-based flexible TEGs so far. Our transparent flexible thin-film p-n junction thermoelectric module with exceptionally high power generation may take a tremendous step forward towards multi-functional wearable devices.