A series of two-dimensional TiX2 (X=Cl, Br, I) monolayers and their corresponding van der Waals heterostructures were predicted by the first-principle calculations. The dynamic and thermodynamic stability of TiX2 (X=Cl, Br, I) monolayers are confirmed by the phonon spectra and molecular dynamics simulations, respectively. The Heyd-Scuseria-Ernzerhof-based band values are 0.311-0.989 eV, showing the tunable transition probability between valence and conduction band. Additionally, the significant visible-light absorption coefficient (~ 105 cm-1) and high power conversion efficiency (~12%) of TiBr2/TiCl2 heterojunctions provide promising potentials for solar cells.
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