Few-layer Bi₂O₂Se: a promising candidate for high-performance near-room-temperature thermoelectric applications

Advancements in high-temperature thermoelectric (TE) materials have been substantial, yet identifying promising near-room-temperature candidates for efficient power generation from low-grade waste heat or TE cooling applications has become critical but proven exceedingly challenging. Bismuth oxyselenide (Bi₂O₂Se) emerges as an ideal candidate for near-room-temperature energy harvesting due to its low thermal conductivity, high carrier mobility and remarkable air-stability. In this study, the TE properties of few-layer Bi₂O₂Se over a wide temperature range (20-380 K) are investigated, where a charge transport mechanism transitioning from polar optical phonon to piezoelectric scattering at 140 K is observed. Moreover, the Seebeck coefficient (S) increases with temperature up to 280 K then stabilizes at∼-200μV K^-1through 380 K. Bi₂O₂Se demonstrates high mobility (450 cm²V^-1s^-1) within the optimum power factor (PF) window, despite itsT-1.25dependence. The high mobility compensates the minor reduction in carrier densityn_2Dhence contributes to maintain a robust electrical conductivity∼3 × 10⁴S m^-1. This results in a remarkable PF of 860μW m^-1K^-2at 280 K without the necessity for gating (V_g= 0 V), reflecting the innate performance of the as-grown material. These results underscore the considerable promise of Bi₂O₂Se for room temperature TE applications.