Effects of halogen elements on a humidity sensor based on a thin film bulk acoustic wave resonator incorporated with Cs3Bi2X9 (X = Cl,Br, I) perovskites

Abstract

All-inorganic perovskites have attracted extensive attention due to their exceptional performance in the realm of optoelectronics. However, there are few reports on the applications of all-inorganic perovskites in humidity detection. This study highlights the applications of thin film bulk acoustic wave resonators (FBARs) integrated with Cs₃Bi₂X₉ (X = Cl, Br, and I) perovskites in humidity sensing. Through comprehensive exploration of the effects of halogen elements, it was found that Cs₃Bi₂Br₉ integrated with FBARs displayed the smallest hysteresis of 6%, a response/recovery time of 130/143 s, reversible repeatability and the highest response of 253 kHz at 85% RH, which was about two times and four times as large as those of the Cs₃Bi₂Cl₉ and Cs₃Bi₂I₉ perovskites integrated with FBARs. These results have demonstrated the feasibility of the FBAR incorporated with perovskites as a promising platform for humidity sensing.