Preparation And Properties Of Novel Photoelectric Materials CH₃NH₃PbX₃?X=I,Br? Single Crystals And Single Crystal Films

Organic-inorganic hybrid perovskite?CH3NH3PbX3?has shown great potential in the development and application of solar cells,photoelectric detection,light emitting diodes fields,because of the advantages of the high optical absorption coefficient,high carrier mobility,adjustable direct band gap,low cost,etc.To optimize the performance of CH₃NH₃PbX₃ optoelectronic devices,it's of great significance to grow CH₃NH₃PbX₃ single crystals and study their basic properties.In this paper,CH3NH3PbI3,CH3NH3PbBr3 single crystals and single crystal thin films were prepared by inversion crystallization method and optimizing spin coating process,respectively.The growth process,structure,optical properties and photoelectric properties were studied.The main results are as follows:?1?CH3NH3PbI3 single crystals were successfully grown in GBL solutions by inversion crystallization method,and the space group is I4/mcm.The edge of CH3NH3PbI3 single crystal UV-Vis-NIR absorption is 827 nm,and the bandgap value is 1.51 eV.The peak of the PL spectrum is 775 nm.After evaporating the Au electrodes on the surface of single crystal,the dark current is 9.72×10^-11 A and the on-off ratio is 10³.?2?CH3NH3PbBr3 single crystals were successfully grown in DMF solutions,and the space group is Pm3m.The crystal size is 8 mm×8 mm×3 mm.The absorption edge of UV-Vis-NIR spectrum is 545 nm,and the bandgap value is 2.27 eV.The peak of the PL spectrum is 539 nm.In the photoelectric performance test of CH3NH3PbBr3 single crystal,the dark current is 1.3×10^-9 A,the light responsivity is 0.67 A/W and the on-off ratio is 10².The rise time of photoelectric response curve is about 200 ms and the falling time is about 250ms.?3?Ultra-thin CH3NH3PbI3 single crystal films were grown on mica substrates by improved spin-coating method.Our improved method is suitable for the growth of ultra-thin single crystal films.Optical photographs show that the films have good surface smoothness and sharp boundary.The thickness of the film was determined by AFM is about 16 nm.The PL spectrum peak of the film's mapping is 766 nm.The dark current is 5.77×10^-12 A,and the I-V curve of the films is consistent with that of single crystal.Only in the low bias range,the current and voltage have a good linear relationship.?4?Ultra-thin CH3NH3PbBr3 single crystal films were also grown by improved spin-coating method.The fluorescence intensity of the boundary of CH3NH3PbBr3 single crystal films is higher.The fluorescence lifetime is about 16 ns confirmed by the time-resolved confocal fluorescence microscopy system.The PL spectrum peak is 509.85 nm.Red shift with the increase of film thickness is observed.The thickness of the films is less than 10 nm measured by AFM.The rise time of the photoelectric response curve is 5.8?s.CH3NH3PbBr3 single crystal film has great potential in the field of micro and low cast detectors.