HfX$_{2}$ (X = Cl, Br, I) Monolayer and Type II Heterostructures with Promising Photovoltaic Characteristics
Xingyong Huang1,2,3, Liujiang Zhou3*, Luo Yan3, You Wang1, Wei Zhang1, Xiumin Xie1, Qiang Xu1, and Hai-Zhi Song1,3*
1Southwest Institute of Technical Physics, Chengdu 610041, China 2Faculty of Science, Yibin University, Yibin 644007, China 3Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China
Abstract：Two-dimensional (2D) materials and their corresponding van der Waals (vdW) heterostructures are considered as promising candidates for highly efficient solar cell applications. A series of 2D HfX$_{2}$ (X = Cl, Br, I) monolayers are proposed, via first-principle calculations. The vibrational phonon spectra and molecular dynamics simulation results indicate that HfX$_{2}$ monolayers possess dynamical and thermodynamical stability. Moreover, their electronic structure shows that their Heyd–Scuseria–Ernzerhof(HSE06)-based band values (1.033–1.475 eV) are suitable as donor systems for excitonic solar cells (XSCs). The material's significant visible-light absorbing capability (${\sim}10^{5}$ cm$^{-1}$) and superior power conversion efficiency (${\sim}$20%) are demonstrated by establishing a reasonable type II vdW heterostructure. This suggests the significant potential of HfX$_{2}$ monolayers as a candidate material for XSCs.
2020, Vol. 37 
