High efficiency Bi2Te3-based thermoelectric materials and devices with energy conversion efficiencies of up to 6.0% under a temperature gradient of 217 K.

Flexible thermoelectrics is a synergy of flexible electronics and thermoelectric energy conversion. In this work, we fabricated flexible full-inorganic thermoelectric power generation modules based on doped silver chalcogenides.

Thermoelectric materials require an optimum carrier concentration to maximize electrical transport and thus thermoelectric performance. Element-doping and composition off-stoichiometry are the two general and effective approaches to optimize carrier concentrations, which have been successfully applied in almost all semiconductors. In this study, we propose a new strategy coined as bonding energy variation to tune the carrier concentrations in Cu2Se-based liquid-like thermoelectric compounds. By utilizing the different bond features in Cu2Se and Cu2S, alloying S at the Se-sites successfully increases the bonding energy to fix Cu atoms in the crystal lattice to suppress the formation of Cu vacancies, leading to much lowered carrier concentrations toward the optimum value. Combing the lowered electrical and lattice thermal conductivities, and the relatively good carrier mobility caused by the weak alloy scattering potential, ultrahigh zTs are achieved in slightly S doped Cu2Se with a maximum value of 2.0 at 1000 K, 30% higher than that in nominallystoichiometric Cu2Se.The table of contents entry: Beyond element-doping and composition off-stoichiometry, we propose a new strategy coined as bonding energy variation to tune the carrier concentrations in Cu2Se-based liquid-like thermoelectric compounds, leading to a maximum zT value of 2.0 at 1000 K, 30% higher than that in nominally-stoichiometric Cu2Se.