Physical performances for six novel Si allotropes in hexagonal 15 and 18 stacking orders

Abstract

Elevating visible light absorption and carrier transport capacity of diamond silicon is a terrifying challenge for improving photoelectric conversion efficiency. Here, six new crystals with similar stacking patterns but various arrangement orders to Si–I are predicated by the random approach combined with group and graph theories. Considering potential applications in the photovoltaic field, we have conducted a detailed study on the stability and physical properties of these structures by first-principles calculations. As a result, these new structures meet mechanical, dynamic, and thermodynamic stabilities, and they are all indirect band gap semiconductor. In particular, among these materials, the effective mass of the smallest hole is only 0.11m0, which is smaller than that of diamond silicon. This result indicates that these structures have better carrier transport capabilities than diamond. In addition, XRD patterns of these six structures were studied for shedding more light for developing these structures in the experiment.