Efficient Solution-Processed n-Type Small-Molecule Thermoelectric Materials Achieved by Precisely Regulating Energy Level of Organic Dopants

To achieve efficient n-type doping, three dopants, 2-Cyc-DMBI-H, A (2-Cyc-DMBI)(2), and (2-Cyc-DMBI-Me)(2), with precisely regulated electron donating ability were designed and synthesized. By doping with a small-molecule 2DQTT-o-OD with high electron mobility, an unexpectedly high power factor of 33.3 mu W m(-1) K-2 was obtained with the new dopant (2-Cyc.DMBI-Me)(2). Notably, with the intrinsically low lateral thermal conductivity of 0.28 W m(-1) K-1, the figure of merit was determined to be 0.02 at room temperature. Thus, we have demonstrated that small molecules with high electron mobility and low-lying LUMO energy levels can achieve high doping efficiency and excellent thermoelectric properties by doping with n-type dopants featuring highly matched energy levels and excellent miscibility.