Prediction of allotropes of tellurium with molecular, one- and two-dimensional covalent nets for photofunctional applications

In the present work, three new semiconducting two-dimensional (2D) Te phases containing three- and four-coordinated Te centers were proposed by using evolutionary algorithms combined with first-principles calculations. Using density functional theory calculations, we discussed the bonding and electronic properties in these phases, and subsequently rationalized their structures. The viability of these predicted structures was demonstrated by evaluating their thermodynamic, dynamic, mechanical, and thermal stabilities. Moreover, a significant direct band gap (0.951-1.512 eV) and excellent transport properties were evidenced in 2D Te nets, which suggests that they could be promising photovoltaic materials candidates. This is further supported by the stability of the associated bulk layered counterparts of the 2D Te nets.