Unconventional Solvent-Doping-Induced Ultrahigh Carrier Mobility Leads to Excellent Thermoelectric Performance in Eco-Friendly Bi2S3 and SnS

Conventional aliovalent doping, which involves replacing host atoms with solute ones, is a well-established strategy in wet chemical synthesis for enhancing semiconductor performance. However, this method faces serious challenges like low solubility and unavoidable carrier mobility loss, which hinder significant performance improvements, particularly in thermoelectrics. Herein, a novel solvent-doping strategy is reported that effectively improves the carrier concentration in nanocrystals by stabilizing cation or anion vacancies. Density functional theory calculations and pair distribution function tests reveal that solvent doping increases the atomic ordering and reduces deformation potential, thereby significantly enhancing carrier mobility. Additionally, the conversion of solvent molecules into carbon contributes to further suppressing the lattice thermal conductivity in substrates. As a result, a record-high peak ZT value of ≈1.0 and a measured thermoelectric conversion efficiency of 1.47% are obtained in solvent-doped Bi₂S₃. Similarly, SnS exhibits a remarkable increase of ≈150% in the peak ZT value following solvent doping. This study demonstrates the application of solvent-doping strategy in thermoelectrics and suggests the potential in other fields, such as transistors, photovoltaic, and catalysis.