A penta-silicene nanoribbon-based 3D silicon allotrope with high carrier mobility and thermoelectric performance.

Motivated by the successful synthesis of penta-silicene nanoribbons using various experimental techniques, we design a new 3D silicon allotrope, labeled cco-Si 48 , by assembling such nanoribbons, confirm its dynamical, thermal and mechanical stabilities, and further study its electron/phonon transport and linear optical properties based on the state-of-the-art theoretical calculations. We find that cco-Si 48 is a direct bandgap semiconductor with a gap of 1.46 eV, exhibiting a high hole mobility in the magnitude of 10 3 cm 2 V -1 s -1 and a low lattice thermal conductivity of 6.33 W m -1 K -1 at 300 K. Unlike the commonly reported n-type silicon-based materials with high thermoelectric performance, the p-type cco-Si 48 outperforms its n-type counterpart in the thermoelectric figure of merit ( ZT ) value with a considerable value of 0.57 at 800 K. We further demonstrate that the electron-phonon interactions play a critical role in determining the optimal carrier concentrations for the peak ZT values. This work expands penta-silicene nanoribbons to their 3D assembled structure with new features and applications.