Transparent charge transfer complex with high thermoelectric performance

Searching for high-performance n-type organic thermoelectric materials with good air stability and high transparency remains a big challenge. Here, we report an all-transparent n-type charge transfer complex [ZnBr₂(Br-C₆H₄-NH₂)₂] with a wide band gap of 4.25 eV. This material exhibits a high electrical conductivity of ∼2,936 S cm⁻¹ and a 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—this 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. These ZT values offer state-of-the-art performance for n-type organic materials that are superior to typical inorganic materials when operating at near room temperature. The high thermoelectric performance is attributed to the electron-transfer-induced n-type heavily doped characteristic, high valley band degeneracy, and heavy effective mass. This work will promote the development of organic thermoelectric materials.