High response and broadband photodetection by monolayer MoSe₂ with vanadium doping and Mo vacancies

Recently, the design of broadband photodetectors based on 2D materials has been a subject of great attention. However, it remains a challenge to achieve both broadband detection and high responsivity for monolayer transition metal dichalcogenide based photodetectors due to the larger band gaps and limited absorption at monolayer thickness. Based on density functional theory calculations, we confirmed that a combination of vanadium substitution doping and Mo vacancies not only decrease the band gap but also enhance the light absorption of monolayer molybdenum diselenide_. We also synthesized MoSe₂ with both V substitution doping and Mo vacancies by chemical vapor deposition and investigated the electrical and photoelectrical properties. Field effect transistor devices based on the materials showed a transition from n- to p-type characteristics and improved carrier mobility with increasing V concentration. Moreover, photodetectors based on monolayer MoSe₂ with 6% V and Mo vacancies displayed a broadband spectral response from 365 nm to 2240 nm, and the responsivity reached 9700 mA W⁻¹ and 2800 mA W⁻¹ at 520 nm and 2240 nm, respectively. Our findings may be useful for designing monolayer transition metal dichalcogenide photodetectors with high responsivities in the infrared region.