# Synthesis, Structure and Photoluminescence Properties of 2D Organic-Inorganic Hybrid Perovskites
## 4 Conclusions  
Four organic-inorganic hybrid perovskites of (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbCl\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\), (C\({}_{6}\)H\({}_{5}\)CH\({}_{2}\)NH\({}_{3}\))\({}_{2}\)PbI\({}_{4}\) and (C\({}_{4}\)H\({}_{9}\)NH\({}_{3}\))\({}_{2}\)PbBr\({}_{4}\) were successfully prepared by solvent evaporation. The crystal structure, surface morphology and optical properties of perovskites materials were studied by X-ray diffraction, transmission electron microscopy, fluorescence spectrophotometer, ultraviolet-visible spectrophotometer and optical confocal microscopy. The effects of different halogens and organic amines on perovskite absorption spectra and PL spectra were investigated. The experimental results show that under the same conditions of organic amines, with the increase of halogen atomic number, halogen radius and corresponding perovskite cell volume increase, perovskite interlayer spacing shows a trend of increasing in turn; the framework of inorganic layer PbX\({}_{2}\) increases in turn, and the forbidden bandwidth of inorganic layer PbX\({}_{2}\) decreases in turn, resulting in the decrease of the exciton binding energy. The binding energy decreases in turn, the peak value of UV-Vis absorption spectra appears to redshift, and the PL lifetime decreases in turn. Under the same inorganic layer, different organic amines will distort the inorganic framework and affect the luminescence properties of perovskite, but organic amines have little effect on the exciton luminescence of perovskites. With the increase of laser power, the two-photon PL intensity of perovskite increases with the increase of laser power, while the PL lifetime decreases with the increase of laser power, mainly the non-geminate recombination. With the development of research on organic-inorganic hybrid perovskite materials, we can prepare hybrid perovskites by changing the composition of inorganic and organic materials, to realize their spectral regulation, promoting better use in solar materials, photoelectric sensors, micro-lasers, and other optoelectronic devices.  
Figure 9: Energy level schemes of the perovskites. VB, valence band; CB, conduction band; ESSs, electron surface defect states; relaxation, the relaxation process; emission, emission process; hv, the energy of a single photon.  
**Author Contributions:** [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] completed the experiments; [PERSON] and [PERSON] wrote the paper; [PERSON], [PERSON] and [PERSON] revised the paper.  
**Funding:** This research was funded by the National Natural Science Foundation of China (Grant No. 11204222); The Natural Science Foundation of Hubei Province, China (Grant No. 2013 CFB316, Grant No. 2014 CFB793); The Innovation Fund of School of Science, Wuhan Institute of Technology (No. CX2016106).  
**Acknowledgments:** The authors would like to thank the support of Lu Peixiang's Group in Huazhong University of Science and Technology.  
**Conflicts of Interest:** The authors declare no conflicts of interest.