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

Graphical By taking advantage of the crystal phase dependent electronic property of SnSe x based materials, SnSe( x %)/SnSe 2 (100− x %) p–n heterostructures were synthesized via a facile one-step colloidal method, and the SnSe(50 %)/SnSe 2 (50 %) based sensor exhibited much improved sensing performance due to the formation of p–n hetero-junctions. 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.