Fabrication of 2D/3D organic-inorganic hybrid perovskite derived materials and its low temperature response to formaldehyde at high humidity

3D organic-inorganic hybrid perovskite derived material FASnI3/SnO2 (HC(NH2)2SnI3/SnO2) is a good kind of gas sensing material for formaldehyde detection. However, it doesn't work well when the relative humidity is above 50 %. To solve this problem, a long-chain 2D perovskite (BA)2SnI4 ((C4H9NH3)2SnI4) is used to modify FASnI3/SnO2 composite due to its hydrophobic character. In this work, FASnI3/(BA)2SnI4 (HC(NH2)2SnI3/ (C4H9NH3)2SnI4) with different ratios of the two materials are first synthesized by a solution method, and then these materials are partially oxidized by controlling the calcination temperature to obtain the FASnI3/(BA)2SnI4/ SnO2(HC(NH2)2SnI3/(C4H9NH3)2SnI4/SnO2) composite. The formaldehyde detection test showed that the response of FASnI3/SnO2 in medium humidity environment can be improved nearly two-thirds times, and the recovery time can be shortened from 183 s to 81 s. Moreover, the response value can reach to 32.5 at high humidity (78 RH%) and keeps unchanged after 24 h of continuous testing at this humidity. All these gas sensing properties improvement can be ascribed to the reason that the introduction of (BA)2SnI4 has led to the formation of the heterojunction and more vacancy oxygen. Of course, the hydrophobic character of FASnI3/(BA)2SnI4 also played an important role.