Tuning electronic and optical properties of monolayer MoS2 by transition metal and nitrogen co-doping

In this work, using first principles study, we systematically studied the doping site, formation energy, electronic and optical properties of transition metal (TM), nitrogen (N) mono-doped and co-doped MoS2. It is found that TM and N atoms tend to settle at Mo and N sites, respectively. Both mono-doping and co-doping can reduce the band gap of MoS2. Mono-doping and co-doping can introduce impurity levels (ILs) within the band gap of MoS2. Especially, Sc-N co-doping positions the ILs in the middle of the band gap of MoS2, which can better assist the photogenerated electronic transitions. More importantly, the additionally added interband transitions can realize infrared light (IR) photoresponse through two-step optical absorption. This work has guiding significance for promoting the applications of MoS2 in the field of IR photodetectors and photovoltaic devices.