Traditional gas sensors are facing the challenge of low power consumption for future application in smart phones and wireless sensor platforms. To solve this problem, self‐powered gas sensors are rapidly developed in recent years. However, all reported self‐powered gas sensors are suffering from high limit of detection (LOD) toward NO₂ gas. In this work, a photovoltaic self‐powered NO₂ gas sensor based on n‐MoS₂/p‐GaSe heterojunction is successfully prepared by mechanical exfoliation and all‐dry transfer method. Under 405 nm visible light illumination, the fabricated photovoltaic self‐powered gas sensors show a significant response toward ppb‐level NO₂ with short response and recovery time and high selectivity at room temperature (25 °C). It is worth mentioning that the LOD toward NO₂ of this device is 20 ppb, which is the lowest of the reported self‐powered room‐temperature gas sensors so far. The discussed devices can be used as building blocks to fabricate more functional Internet of things devices.

Novel S,N-codoped hydrophobic carbon dots (S,N-OCDs) were directly fabricated into a white light-emitting-diode (WLED), which showed excellent color rendering properties.