Revisiting the thermoelectric transport of monolayer InP3 with full ab initio calculations

Thermoelectric materials facilitate the mutual conversion of thermal energy and electric energy, representing environmentally friendly candidates for power generation. Consequently, there is significant interest in two-dimensional materials due to their potential for achieving superior thermoelectric performance when compared to their bulk counterparts. However, theoretical overestimations are prevalent for many of them, which originates from the fact that most theoretical studies have utilized a constant relaxation time within the framework of a single-mode deformation potential theory (DPT). In this work, we take monolayer $\mathrm{In}{\mathrm{P}}_{3}$ as an example to systematically revisit its thermoelectric transport by using parameter-free ab initio calculations combined with the Boltzmann transport equation. It is found that the scatterings from longitudinal acoustic phonons to charge carriers are not the most influential ones in monolayer $\mathrm{In}{\mathrm{P}}_{3}$, manifesting that the scattering rates are significantly underestimated within the crude approximation of single-mode DPT. By considering the state-dependent electron-phonon scattering rates, the monolayer $\mathrm{In}{\mathrm{P}}_{3}$ is found to have room-temperature maximum $\mathit{ZT}$ values of 0.37 and 0.18 for $n$- and $p$-type doping, respectively, which are one order of magnitude smaller than those predicted using a constant scattering rate from single-mode DPT. We demonstrate that conventional methods like single-mode DPT do not adequately describe the thermoelectric properties of monolayer $\mathrm{In}{\mathrm{P}}_{3}$. To calculate the thermoelectric transport of monolayer $\mathrm{In}{\mathrm{P}}_{3}$ properly, one needs to consider the scatterings from all phonons. We not only uncover the underlying mechanisms governing thermoelectric transport, but also offer a paradigm approach to accurately predict the thermoelectric transport with less computation cost.