Energy-Filtered Acceleration of Charge-Carrier Transport in Organic Thermoelectric Nanocomposites

Nanocomposite systems have notably improved the thermoelectric (TE) figure-of-merit ZT of organic materials; however, further studies are required to reveal the underlying TE charge transport in the heterogeneous organic system. Here, the relationship between the TE properties and the energy structure of the organic TE nanocomposite is investigated by developing different internal potential steps in poly­(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) with carbon quantum dots (CQDs) of tunable electronic bands. The charge transport across the insulating PSS layer was facilitated by embedded CQDs, which accelerated the high-energy hole transport and increased both the Seebeck coefficient and the electrical conductivity. With a carefully tuned internal potential step, PEDOT:PSS/CQD nanocomposite showed a power factor of 584 μW m–1 K–2, which was 3 times larger than that of pristine PEDOT:PSS and yields a high ZT = 0.32. This work provides a fresh perspective on the energy-filtering effect for the design of high-performance organic TE nanocomposites.