Tuning the Thermoelectric Performance of Two‐Dimensional GeIBr via External Electric Field and Layer Number: A First‐Principles Study

Thermoelectric materials with high energy conversion efficiency are of considerable interest for addressing the energy crisis and environmental issues. In this work, first‐principles calculations were performed to systematically investigate the effects of an external electric field and variation in layer number on the electronic structure and thermoelectric performance of the GeIBr monolayer. GeIBr is identified as an indirect‐band‐gap semiconductor with a band gap of 2.15 eV, and its mechanics and dynamical stabilities are confirmed by the elastic constant and phonon spectrum calculations. The external electric field has only a limited influence on the band gap. A weak electric field of 0.3 V/Å induces little change in the thermoelectric figure of merit ( ZT ), whereas a strong electric field of 0.6 V/Å significantly enhances the thermoelectric performance, increasing the ZT value from 2.06 to 5.52 at 900 K. Moreover, increasing the layer number reduces the band gap to 1.83 eV. Although the bilayer structure lowers the ZT value of the n ‐type system, it markedly enhances the thermoelectric performance of the p ‐type system, with the ZT value increasing from 2.06 to 3.60 at 900 K. These findings demonstrate that GeIBr is a promising thermoelectric material, whose thermoelectric performance can be effectively improved by external electric‐field tuning and changes in layer number.