The Study On The Stability Of CH₃NH₃PbI₃ Film In Different Humidity

This thesis studied the degradation process of CH₃NH₃PbI₃ film at 15%, 50% and 90% RH three different humidity environments.The main conclusion of the study is divided into two parts:?1?In the study on the stability of CH₃NH₃PbI₃ film, we studied the construction and degradation products in CH₃NH₃PbI₃ film during the degradation processes by using UV-visible absorption spectroscopy, steady-state fluorescence spectroscopy, XRD detection technology. The results showed that the full width at half maximum?FWHM? of the fluorescence spectrum film decreased over degradation time, it mean that the construction became smooth and highly ordered because the water molecules acted on the CH3NH3 Pb I3; Film center wavelength?CWL? of fluorescence spectra and the peak position of XRD characteristic occurred blue shift and increase respectively, it mean the crystal phase transferred from tetragonal to cubic in degradation process; Absorption spectra and XRD patterns show that Pb I2 is the major degradation product, and NH3-related component was likely generated in 50% RH humidity environment. The CH3NH3 Pb I3 hydrate was synthesized as an intermediates in 90% RH humidity environment; In three humidity environments, decay rate of the intensity of CH₃NH₃PbI₃ film absorption spectral characteristic peaks show that high humidity cause degradation rate becomes faster.?2? We have tested the photoexcitation carriers dynamics in the film?s degradation process by the self-built microwave dielectric spectroscopy detection system in laboratory. It summarized the relationship between the carrier lifetime with the degradation time. In this experiment, In order to satisfy the measurement requirement of CH₃NH₃PbI₃ PbI3 film, we made the following improvement to the microwave dielectric spectroscopy detection system:?1?Increasing the size of the cavity slit;?2?Improving the energy efficiency of the sample excitation light;?3?The gaseous environment of sample measurement can be controlled.After the equipment improved, it can measure the solid substrate samples within the range of 12mm*2mm in different atmospheres, and the accuracy and reliability of the results were improved. Results of carrier dynamics in CH₃NH₃PbI₃ film?s show that free carrier lifetime increase and then decline in 15% and 50%RH humidity environment, and the free carrier lifetime had a decreasing tendency. The increase of the free carrier lifetime maybe due to the formation of shallow electron traps in the degradation process, while the decrease of the free carrier lifetime maybe of the formation of deep electron traps during this period.