Thermoelectric and Photothermoelectric Properties of Nanocomposite Films Based on Polybenzimidazole and Carbon Nanotubes

We herein report the thermoelectric and photothermoelectric properties of polybenzimidazole (PBI)-based nanocomposite films with 1–20 wt % multiwalled carbon nanotube (MWCNT) loadings, which are manufactured by a facile solution casting method. The thermoelectric characterization, which is carried out at temperature differences of up to 40 K between both film ends, reveals that the Seebeck coefficient of the nanocomposite films increases from ∼29 to ∼36 μV/K with increasing MWCNT content from 1 to 20 wt % and that the thermoelectric current generation efficiency changes from ∼1 nA/K at 1 wt % MWCNT to ∼84 nA/K at 10 wt % MWCNT to ∼28 nA/K at 20 wt % MWCNT. The visible light illumination at the interface between the nanocomposite film and the silver electrode induces excellent photothermoelectric performance in terms of temperature increment (ΔTPT), voltage generation (VPTE), and electric current generation (APTE), which are dependent on the MWCNT content and visible light wavelength. For instance, the PBI nanocomposite film with 10 wt % MWCNT can attain ΔTPT of ∼33 °C, VPTE of ∼267 μV, and APTE of ∼234 nA under the visible light illumination of 520 nm wavelength and 8.87 W/cm2 power density at the interface between the film and the electrode. This excellent photothermoelectric performance of PBI/MWCNT nanocomposite films enables potential materials for advanced applications of energy harvesting and sensing from visible light and heat.