Thermoelectric thiophene dendrimers with large Seebeck coefficients

π-Conjugated dendrimers are emerging platforms for molecular-based photonics and electronics. Herein, we demonstrate thiophene dendrimers as new thermoelectric (TE) materials with large Seebeck coefficients through chemical charge-carrier doping, conducting film preparation, and TE transport evaluations (electrical conductivity and Seebeck coefficient). Complementary characterization with absorption, photoelectron spectroscopy, and molecular calculations reveals that the highly degenerate frontier molecular orbital energy levels derived from the highly branched and symmetric molecular structures of the dendrimers play an important role in the anomalously large Seebeck coefficients based on Mott's equation. With the recent rapid progress in the technologies for synthesizing π-conjugated dendrimers and molecular designing flexibilities, our results propose a novel strategy for exploring new TE materials. π-Conjugated dendrimers are emerging platforms for molecular-based photonics and electronics.