Gate-tunable Polar Optical Phonon to Piezoelectric Scattering in Few-layer Bi2O2Se for High Performance Thermoelectrics

Abstract

Atomically thin Bi2O2Se has emerged as a new member in two-dimensional (2D) materials with ultra-high carrier mobility and excellent air-stability, showing great potential for electronics and optoelectronics. In addition, its ferroelectric nature renders ultra-low thermal conductivity, making it a perfect candidate for thermoelectrics. In this work, we experimentally investigate the thermoelectric performance of 2D Bi2O2Se over a wide temperature range (20 - 300 K). We observe a gate-tunable transition from polar optical phonon (POP) scattering to piezoelectric scattering, which facilitates the capacity of drastic mobility engineering in 2D Bi2O2Se. Consequently, high power factor of more than 400 uWm-1K-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 performances by changing scattering mechanisms and carrier mobility over a wide temperature range.