Direct/indirect band gap tunability in van der Waals heterojunctions based on ternary 2D materials Mo1-xWxY2

Artificial van der Waals (vdW) heterojunctions assembled by atomically-thin two-dimensional (2D) materials have demonstrated new physical phenomena and unusual properties, thus triggering new electronic, optoelectronic, valleytronic and photocatalytic application. Herein, the electronic band structures of different vdW heterojunctions based on ternary Mo1-xWxY2 (Y = S, Se; x = 0-1) monolayer with five stacking orders (AA, AA', A'B, AB, AB') have been investigated using first principle calculations. The direct/indirect band gap has been obtained in the AA' stacking type-II heterojunctions, ranging from 0.538 eV to 1.260eV, that are determined by the interlayer distances and stoichiometries. The estimated power conversion efficiency of the AA' stacking type-II heterojunction varied from 9.1% to 23.4%. The type-I heterojunctions have also been predicted when semiconducting 2H-MoTe2 monolayer stacks with the specific Mo1-xWxSe2 monolayer, which are MoTe2/Mo0.25W0.75Se2 and MoTe2/Mo0.5W0.5Se2. The reported theoretical results can provide broader 2D materials design possibility for the functional devices.