Theoretical design of two-dimensional carbon nitrides

The study of two-dimensional (2D) materials has attracted considerable attention owing to their unique but fascinating properties. Here we systematically explored 2D carbon nitride monolayer sheets via the particle swarm optimization algorithm in combination with density functional theory. As a result of structural searches, four carbon nitride monolayers are predicted with stable stoichiometries of C5N2, C2N, C(3)N(2)and CN. These predicted structures are semiconductors with an optimal band gap for solar cell application as indicated in our electronic simulations. Our current results also reveal the high tensile strengths of the predicted structures compared to known porous carbon nitride monolayer sheets. This work may provide a route for the design of 2D candidates in the application of photovoltaic materials.