Exceptional Radiation Absorption in a Pentagon-Based Si Allotrope.

Lopez-Bezanilla, Alejandro; Littlewood, Peter B · Nano Lett · 2021

basic_science · Level V

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Abstract

Excellent photovoltaic performance is predicted in a pentagonal covalent network of Si in a hollow structure exhibiting both thermal and dynamical stability. Consisting of a combination of sp<sup>2</sup> and sp<sup>3</sup> hybridized Si atomic orbitals, the GW0 computed band structure shows an indirect band gap near the zone edge and also a manifold of directly absorbing transitions at frequencies in the window of visible light, in distinction with conventional Si. Hydrogenation of a single sp<sup>2</sup> site is predicted to lead to a robust local magnetic moment. We find a low formation energy at low pressure that is compatible with other experimentally known phases, suggesting that a stable phase might be obtained.