Thermoelectric properties of Bi₂O₂Se single crystals

Bismuth oxyselenide (Bi$_2$O$_2$Se) attracts great interest as a potential n-type complement to p-type thermoelectric oxides in practical applications. Previous investigations were generally focused on polycrystals. Here, we performed study the properties of Bi$_2$O$_2$Se single crystals. Our samples exhibit electron mobility high 250 cm$^2.$V$^{-1}$.s$^{-1}$ and thermal conductivity low $2$ W.m$^{-1}$.K$^{-1}$ near room temperature. The maximized figure merit is yielded be 0.188 at 390 K, higher than that Consequently, rough estimation phonon mean free path ($\ell_\textrm{ph}$) from kinetic model amounts 12 $\r{A}$ K follows $T^{-1}$ behavior. An extrapolation $\ell_\textrm{ph}$ temperatures indicates this system approaches Ioffe-Regel limit about 1100 K. In light dispersions, argue ultralow attributed intense anharmonic phonon-phonon scattering, including Umklapp process acoustic optical scattering. results suggest crystals provide further improvement performance Bi$_2$O$_2$Se.