Light enhanced room temperature resistive NO2 sensor based on a gold-loaded organic-inorganic hybrid perovskite incorporating tin dioxide.

A material is described for sensing NO2 in the gas phase. It has an architecture of type Au/MASnI3/SnO2 (where MA stands for methylammonium cation) and was fabricated by first synthesizing Au/MASnI3 and then crystallizing SnO2 on the surface by calcination. The physical and NO2 sensing properties of the composite were examined at room temperature without and with UV (365 nm) illumination, and the NO2-sensing mechanism was studied. The characterization demonstrated the formation of a p-n heterojunction structure between p-MASnI3 and n-SnO2. The sensor, best operated at a voltage of 1.1 V at room temperature, displays superior NO2 sensing performance. Figures of merit include (a) high response (Rg/Ra = 240 for 5 ppm NO2; where Rg stands for the resistance of a sensor in test gas, and Ra stands for the resistance of a sensor in air), (b) fast recovery (about 12 s), (c) excellent selectivity compared to sensors based on the use of SnO2 or Au/SnO2 only, both at room temperature under UV illumination; (d) a low detection limit (55 ppb), and (e) a linear response between 0.5 and 10 ppm of NO2. The enhanced sensing performance is mainly attributed to the high light absorption capacity of MASnI3, the easy generation and transfer of photo-induced electrons from MASnI3 to the conduction band of SnO2, and the catalytic effect of gold nanoparticles. Graphical abstract Schematic of the energy band diagrams of the gold-functionalized MASnI3/SnO2 system after equilibrium with UV illumination, by which the enhanced sensing performance for NO2 can be explained.