Prediction of two-dimensional C 3 N 2 semiconductors with outstanding stability, moderate band gaps, and high carrier mobility.

Two-dimensional (2D) semiconductors with suitable band gaps, high carrier mobility, and environmental stability are crucial for applications in the next generation of electronics and optoelectronics. However, current candidate materials each have one or more issues. In this work, two novel C 3 N 2 monolayers, P-C 3 N 2 and I-C 3 N 2 are proposed by first-principles calculations. Both structures have demonstrated excellent dynamical and mechanical stability, with thermal stability approaching 3000 K. Importantly, P-C 3 N 2 shows a distinct advantage in formation energy compared to currently synthesized 2D carbon nitride materials, indicating its potential for experimental synthesis. Electronic structure calculations reveal that both P-C 3 N 2 and I-C 3 N 2 are intrinsic semiconductors with moderate band gaps of 2.19 and 1.81 eV, respectively. Additionally, both C 3 N 2 monolayers display high absorption coefficients up to 10 5 cm -1 , with P-C 3 N 2 showing significant absorption capabilities in the visible light region. Remarkably, P-C 3 N 2 possesses an ultra-high carrier mobility of up to 10 4 cm 2 V -1 s -1 . These findings provide theoretical insights and candidates for future applications in the electronics and optoelectronics fields.