Gate-Tunable Polar Optical Phonon to Piezoelectric Scattering in Few-Layer Bi₂ O₂ Se for High-Performance...

Atomically thin Bi₂ O₂ Se has emerged as a new member in 2D materials with ultrahigh carrier mobility and excellent air-stability, showing great potential for electronics and optoelectronics. In addition, its ferroelectric nature renders an ultralow thermal conductivity, making it a perfect candidate for thermoelectrics. In this work, the thermoelectric performance of 2D Bi₂ O₂ Se is investigated over a wide temperature range (20-300 K). A gate-tunable transition from polar optical phonon (POP) scattering to piezoelectric scattering is observed, which facilitates the capacity of drastic mobility engineering in 2D Bi₂ O₂ Se. Consequently, a high power factor of more than 400 µW m^-1  K^-2 over an unprecedented temperature range (80-200 K) is achieved, corresponding to the persistently high mobility arising from the highly gate-tunable scattering mechanism. This finding provides a new avenue for maximizing thermoelectric performance by changing the scattering mechanism and carrier mobility over a wide temperature range.