Low-energy silicon allotropes with strong absorption in the visible for photovoltaic applications

摘要

We present state-of-the-art first-principle calculations of the electronicand optical properties of silicon allotropes with interesting characteristicsfor applications in thin-film solar cells. These new phases consist ofdistorted sp$^3$ silicon networks and have a lower formation energy than otherexperimentally produced silicon phases. Some of these structures turned out tohave quasi-direct and dipole-allowed band gaps in the range 0.8--1.5\,eV, andto display absorption coefficients comparable with those of chalcopyrites usedin thin-film record solar cells.