Research On The Gas Sensing Performance Of The Perovskite Materials

Perovskite materials are expected to be used in efficient gas sensors due to their advantages of low cost,easy synthesis,high carrier mobility and bipolar charge transfer.At present,perovskite gas sensor has been proved to have high response to NH3,NO2 and other polar gases.However,its further application is seriously restricted due to the low environmental stability of traditional organic-inorganic hybrid perovskite material.In this paper,a variety of perovskite gas sensors were prepared and their gassensing performance to formaldehyde(HCHO)gas was studied.On the basis of the above research,the δ-CsPbI2.6Br0.4 gas sensor was prepared by in-situ growth method.The effects of the concentration of precursor solution and heat treatment temperature on the gas-sensing performance were investigated,and the optimal conditions for the preparation of δ-CsPbI2.6Br0.4 gas sensor were determined.We studied the sensitivity,response-recovery time,reproducibility and selectivity of the δ-CsPbI2.6Br0.4 gas sensor to HCHO,and preliminatively revealed the mechanism of the interaction between theδ-CsPbI2.6Br0.4 gas sensor and formaldehyde,mainly carried out the following studies:(1)δ-CsPbI2.6Br0.4,Cs2PbI2(SCN)2,and MA3BI2I9 were used to prepare gas sensor and their gas-sensing performance were analyzed.It was found that δ-CsPbI2.6Br0.4 gas sensor has the highest response to formaldehyde.Based on above research,the followup research is carried out;(2)By studying the effects of the concentration of precursor solution and heat treatment temperature on the gas-sensing performance,we found that the film presented the fiber surface that is favorable for gas-sensing performance when the concentration of 0.6M and the heat treatment temperature of 340℃.The sensitivity of gas sensor increases with the increase of formaldehyde concentration,and the gas sensor displayd a quicker response-recovery time(the response time:40s,the recovery time:43s),excellent reproducibility and selectivity;(3)Combined with the experimental results,we have carried out theoretical calculation and analyzed the mechanism of the interaction between δ-CsPbI2.6Br0.4 and formaldehyde:before formaldehyde contacts with the gas sensor,oxygen in the air is adsorbed into the gas sensor,capturing electrons in the semiconductor conduction band and converting them into Oads(O-2ads,O-ads,O2-ads),the concentration of electrons in the conduction band decreases and the device resistance increases.Subsequently,when the gas sensor is placed in a formaldehyde atmosphere,the O-atoms of the HCHO gas combined with the Cs-atoms of δ-CsPbI2.6Br0.4,the formaldehyde is converted from the gaseous state to the adsorbed state,reacting with the adsorbed oxygen to form CO2 and H2O.Electrons are released and enter the conduction band of δ-CsPbI2.6Br0.4.As a result,the electron concentration in the conduction band increases and the device resistance decreases.