Gate‐Tunable Polar Optical Phonon to Piezoelectric Scattering in Few‐Layer Bi 2 O 2 Se for High‐Performance Thermoelectrics

Atomically thin Bi 2 O 2 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 Bi 2 O 2 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 Bi 2 O 2 Se. Consequently, a high power factor of more than 400 µ W 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.