Transparent Charge Transfer Complex with High Thermoelectric Performance

Abstract Searching n-type high-performance organic thermoelectric material with good air-stability and high transparency remains a big challenge. Here, we report an all-transparent n-type charge transfer complex [ZnBr 2 (Br-C 6 H 4 -NH 2 ) 2 ] with an ultra-wide band gap of 4.25 eV (~ 163 k B T ). This material exhibits an ultrahigh electrical conductivity of ~ 2,936 S cm − 1 and a high Seebeck coefficient of − 114 µV K ‒1 , leading to an extraordinarily high power factor of ~ 3,797 µW m ‒1 K ‒2 at room temperature, which is a record value for organic thermoelectric materials. Remarkably, figure-of-merit (ZT) values of 0.23 at 298 K and 0.45 at 473 K were achieved, respectively. The ZT values are not only the state-of-the-art performance for n-type organic thermoelectric materials, but also better than those of some typical inorganic thermoelectric materials at near room-temperature range. The extraordinarily high thermoelectric performance is attributed to the electron transfer induced n-type heavily doped characteristic, high valley band degeneracy and heavy effective mass. Owing to its exceptional thermoelectric performance and excellent air-stability, [ZnBr 2 (Br-C 6 H 4 -NH 2 ) 2 ] can be considered as a milestone in the development of organic thermoelectric materials.