Thermoelectric Enhancement in Single Organic Radical Molecules

Abstract

Organic thermoelectric materials have potential for wearable heating, cooling, and energy generation devices at room temperature. For this to be technologically viable, high-conductance (<i>G</i>) and high-Seebeck-coefficient (<i>S</i>) materials are needed. For most semiconductors, the increase in <i>S</i> is accompanied by a decrease in <i>G</i>. Here, using a combined experimental and theoretical investigation, we demonstrate that a simultaneous enhancement of <i>S</i> and <i>G</i> can be achieved in single organic radical molecules, thanks to their intrinsic spin state. A counterintuitive quantum interference (QI) effect is also observed in stable Blatter radical molecules, where constructive QI occurs for a <i>meta</i>-connected radical, leading to further enhancement of thermoelectric properties. Compared to an analogous closed-shell molecule, the power factor is enhanced by more than 1 order of magnitude in radicals. These results open a new avenue for the development of organic thermoelectric materials operating at room temperature.