Solution‐Processed p‐SnSe/n‐SnSe2 Hetero‐Structure Layers for Ultrasensitive NO2 Detection

Abstract The formation of semiconductor heterostructures is an effective approach to achieve high performance in electrical gas sensing. However, such heterostructures are usually prepared via multi‐step procedures. In this contribution, by taking advantage of the crystal phase‐dependent electronic property of SnSe x based materials, we report a one‐step colloid method for the preparation of SnSe( x %)/SnSe 2 (100− x %) p–n heterostructures, with x ≈30, 50, and 70. The obtained materials with solution processability were successfully fabricated into NO 2 sensors. Among them, the SnSe(50 %)/SnSe 2 (50 %) based sensor with an active layer thickness of 2 μm exhibited the highest sensitivity to NO 2 (30 % at 0.1 ppm) with a limit of detection (LOD) down to 69 ppb at room temperature (25 °C). This was mainly attributed to the formation of p–n junctions that allowed for gas‐induced modification of the junction barriers. Under 405 nm laser illumination, the sensor performance was further enhanced, exhibiting a 3.5 times increased response toward 0.1 ppm NO 2 , along with a recovery time of 4.6 min.