Thermoelectric Performance of Donor-Acceptor-Donor Conjugated Polymers Based on Benzothiadiazole Derivatives

Donor-acceptor-donor conjugated polymers are superior to other thermoelectric organic materials because it is much easier to modify their structure to reduce the bandgap between the conduction and valence bands, which is desirable for thermoelectric materials with high Seebeck coefficients. Despite this, studies of the thermoelectric performance of donor-acceptor-donor conjugated polymers are rare. In this study, four low-bandgap donor-acceptor-donor conjugated polymers, poly(4,7-bis(2,3-dihydrothieno[3,4-b][1,4] dioxin-5-yl)benzo[c][1,2,5]thiadiazole) (PEBTE), poly(4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)benzo[c][1,2,5]selenadiazole) (PEBSeE), poly (4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-[1,2,5]thiadiazolo [3,4-c] pyridine) (PEPTE), and poly(4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-[1,2,5]selenadiazolo[3,4-c]pyridine) (PEPSeE), were deposited by electrochemical polymerization of 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)benzo[c][1,2,5]thiadiazole (EBTE), 4,7-bis(2,3-dihydro-thieno[3,4-b][1,4] dioxin-5-yl)benzo[c][1,2,5]selenadiazole (EBSeE), 4,7-bis(2,3-dihydrothieno [3,4-b][1,4]dioxin-5-yl)-[1,2,5]thiadiazolo[3,4-c] pyridine (EPTE) and 4,7-bis (2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-[1,2,5] selenadiazolo[3,4-c]pyridine (EPSeE), respectively and their thermoelectric performance was investi- gated. Compared with polyselenophenes, PEBTE and PEBSeE in pressed pellets had higher electrical conductivity (10(-1)-10(1) S cm(-1)) but lower Seebeck coefficient (14.0 mu V K-1) at room temperature. Future work may focus on treatment of these donor-acceptor-donor polymers to improve their electrical conductivity and Seebeck coefficient, and further investigation of their thermoelectric performance.