High Anisotropic Optoelectronics in Monolayer Binary M₈X₁₂ (M = Mo, W; X = S, Se, Te)

Exploring high performance and excellent ambient stability in two-dimensional (2D) monolayer photoelectric materials is motivated by not only practical applications but also scientific interest. Here, a new 2D monolayer W₈Se₁₂ structure is synthesized via in situ electron-beam irradiation on 2D WSe₂. Moreover, we systematically studied the photoelectric properties of the class of monolayer M₈X₁₂ (M = Mo, W; X = S, Se, and Te) materials by first principles. The results indicated that Mo₈S₁₂, Mo₈Se₁₂, W₈S₁₂, and W₈Se₁₂ monolayers possess desirable direct band gaps and remarkable anisotropic optical absorption in visible light, while Mo₈Te₁₂ and W₈Te₁₂ monolayers are metals. Impressively, the monolayer W₈Se₁₂ can result in a direct-indirect-metal transition under uniaxial strain. In addition, they show high anisotropic carrier mobilities (up to 10⁴ cm² V^-1 s^-1), significantly over those of transition-metal dichalcogenides. These new binary monolayer M₈X₁₂ structures can effectively broaden the 2D material family and may provide four potential candidates in photoelectric applications.