Promoting Room-Temperature n-type Bismuth Telluride Thermoelectrics via High-Potential Barrier Heterointerfaces

The donor effect of polycrystalline n-type bismuth telluride (Bi₂Te₃) during sample preparation usually results in the peak thermoelectric figure of merit (ZT) at temperatures above 400 K, severely restricting its application in the room-temperature (RT) range. A leap in RT performance requires innovative strategies that replace conventional methods of regulating point defects with limited effectiveness. We demonstrate excellent thermoelectric performance with an RT figure of merit, ZT = 1.2, and a maximum ZT = 1.3 at 325 K, by regulating the high-potential barrier heterointerfaces composed of La₂O₃ nanoparticles (NPs) and Bi₂Te_2.7Se_0.3 (BTS). The created energy barriers at grain boundaries scatter and localize carriers through O–Bi ionic bonding and O–Te hybridization, enhancing the density of states in adjacent regions and leading to a rapid rise in the RT Seebeck coefficient (from 148.67 μV K^–1 to 222.84 μV K^–1 at 300 K). Another aspect of La₂O₃ NPs, as the second term of nano-oxide, introduces multiscale defect-scattering phonons, thereby enhancing thermal performance. Finally, at temperature difference ΔT = 10 K, a maximum output voltage and power, V_max = 239.73 mV and P_max= 10.50 mW, can be achieved with the fabricated TE module. Our findings underscore the full potential for promoting the performance of thermoelectric materials in the lower temperature region via high-energy barrier interface engineering.