Light enhanced room temperature resistive NO sensor based on a gold-loaded organic-inorganic hybrid perovskite incorporating tin dioxide.

A material is described for sensing NO in the gas phase. It has an architecture of type Au/MASnI/SnO (where MA stands for methylammonium cation) and was fabricated by first synthesizing Au/MASnI and then crystallizing SnO on the surface by calcination. The physical and NO sensing properties of the composite were examined at room temperature without and with UV (365 nm) illumination, and the NO-sensing mechanism was studied. The characterization demonstrated the formation of a p-n heterojunction structure between p-MASnI and n-SnO. The sensor, best operated at a voltage of 1.1 V at room temperature, displays superior NO sensing performance. Figures of merit include (a) high response (R/R = 240 for 5 ppm NO; where R stands for the resistance of a sensor in test gas, and R 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 SnO or Au/SnO 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 NO. The enhanced sensing performance is mainly attributed to the high light absorption capacity of MASnI, the easy generation and transfer of photo-induced electrons from MASnI to the conduction band of SnO, and the catalytic effect of gold nanoparticles. Graphical abstract Schematic of the energy band diagrams of the gold-functionalized MASnI/SnO system after equilibrium with UV illumination, by which the enhanced sensing performance for NO can be explained.