**5. Conclusions**

In this work, we present investigation on the humidity properties on the MAPbI3 based sensor. The results show that the sensor exhibits high sensitivity, superior to that of many perovskite materials. The humidity performances were argued to be caused by the fact that water molecules entered the perovskite lattice, serving as a strong *n*-type dopant that greatly enhances the concentration of conductive electrons. Our results emphasize that the MAPbI3 perovskite has a great promise as humidity sensing material and could have widespread applications in humidity sensor.

**Author Contributions:** Conceptualization, X.Z. and Y.S.; methodology, S.L.; software, P.C.; validation, X.Z., Y.S. and S.L.; formal analysis, G.C.; investigation, X.Z.; resources, J.W.; data curation, X.Z.; writing—original draft preparation, X.Z.; writing—review and editing, C.W.; visualization, W.C.; supervision, C.W.; project administration, X.Z.; funding acquisition, C.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by National Natural Science Foundation of China, grant number 51872001 and 12174001.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data is available on reasonable request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
