  Lead chalcogenides are the promising thermoelectric (TE) materials having
narrow band gap. The present work investigates the TE behaviour of PbSe in the
temperature range 300-500 K. The transport properties of the sample have been
studied using the Abinit and BoltzTrap code. The experimentally observed value
of \textit{S} at 300 and 500 K is found to be $\sim$ 198 and 266 $\mu$V
K$^{-1}$, respectively. The rate of increase in \emph{S} from 300 to 460 (460
to 500) K is found to be $\sim$ 0.4 (0.09). The temperature dependent
electrical conductivity \textit{($\sigma$)} shows the increasing trend, with
values of $\sim $ 0.35 $\times $ 10$^{3}$ and $\sim$ 0.58 $\times$ 10$^{3}$
$\Omega$$^{-1}$ m$^{-1}$ at 300 and 500 K, respectively. Further, the value of
thermal conductivity \textit{($\kappa$)} at 300 (500) K is found to be 0.74
(1.07) W m$^{-1}$ K$^{-1}$. The value of \textit{$\kappa$} is found to be
increasing upto 460 K and then starts decreasing. The dispersion plot indicates
that PbSe is a direct band gap semiconductor with band gap value of 0.16 (0.27)
eV considering spin-orbit coupling (without SOC). The partial density of states
(PDOS) plot shows that Pb 6p and Se 4p states have a major contribution in the
transport properties. The observed and calculated values of \textit{S} gives a
good match for SOC case. The calculated \textit{$\sigma$} and electronic part
of thermal conductivity (\textit{$\kappa{_e}$}) gives good match with the
experimental data. The maximum power factor (PF) value of $\sim$ 4.3 $\times$
10$^{-5}$ W/mK$^{2}$ is observed at 500 K. This work helps in understanding the
TE behaviour of PbSe through a novel and insightful alliance of experimental
measurements and DFT approach.
