MoS2 Van der Waals p–n Junctions Enabling Highly Selective Room‐Temperature NO2 Sensor

Abstract Van der Waals p–n junctions of 2D materials present great potential for electronic devices due to the fascinating properties at the junction interface. In this work, an efficient gas sensor based on planar 2D van der Waals junctions is reported by stacking n‐type and p‐type atomically thin MoS 2 films, which are synthesized by chemical vapor deposition (CVD) and soft‐chemistry route, respectively. The electrical conductivity of the van der Waals p–n junctions is found to be strongly affected by the exposure to NO 2 at room temperature (RT). The MoS 2 p–n junction sensor exhibits an outstanding sensitivity and selectivity to NO 2 at RT, which are unavailable in sensors based on individual n‐type or p‐type MoS 2 . The sensitivity of 20 ppm NO 2 is improved by 60 times compared to a p‐type MoS 2 sensor, and an extremely low limit of detection of 8 ppb is obtained under ultraviolet irradiation. Complete and very fast sensor recovery is achieved within 30 s. These results are superior to most of the previous reports related to NO 2 detection. This work establishes an entirely new sensing platform and proves the feasibility of using such materials for the high‐performance detection of gaseous molecules at RT.