| Since the beginning of the 21st century,with the rapid consumption of fossil fuels and the destruction of the environment that human beings have depended on for their own survival,the traditional supply of old energy is increasingly difficult to adapt to the rapid development trend of the current society.Therefore,people are working diligently to find an energy source that is both efficient and relatively clean in order to ease the current severe energy situation.Solar energy is a kind of clean energy that can be used and can be inexhaustible.It provides an effective way to solve the energy shortage in the future.Organic-inorganic hybrid perovskite solar cells have become one of the hot spots in the field of photovoltaic research due to their high photoelectric conversion efficiency and low cost.In a few short years,through the unremitting efforts of many researchers,perovskite solar cells have been rapidly developed.Therefore,inorganic-organic hybrid solar energy technology has broad prospects for development.Compared to polycrystalline and thin films,perovskite single crystals have superior crystallinity,more stable structure,and better optoelectronic properties than polycrystalline films.They also show unique properties in terms of characterization,such as obvious absorption edges.Redshift and so on.In order to systematically study the photoelectric properties of organic-inorganic hybrid perovskite single crystals,a large-size perovskite single crystal was designed and grown in this thesis,and a planar photodetector was used to study its photoelectric properties.This article mainly studied the growth of lead methylamine iodide and lead bromide crystals,as well as their optical and optoelectronic properties.First,the synthesized methyl iodide and lead iodide were dissolved in butyrolactone,and large-sized CH3NH3PbI3 crystals were grown by inversion method.The interface growth mechanism was studied by AFM;XRD,absorption spectra,fluorescence spectra,etc.were used.Its crystal structure and optical properties were studied.Photodetectors based on(100)and(112)crystal faces were prepared using interdigitated electrodes and their optoelectronic properties were studied.The study found that there are different height growth steps on the(100)surface of the CH3NH3IPbX3 single crystal,the height of the basic growth step is equal to the height of the half cell?and the basic growth step is generated by the screw dislocation;the supersaturation of the solution is increased,and the growth steps are coalesced.And agglomerating steps are an even number of basic growth steps.The single crystal of CH3NH3PbX3 grown belongs to the tetragonal system and the space group is:14/mcm.the unit cell parameters are a=b=8.8579 A,c=12.656 A and the band gap is 1.48 eV.The growth of crystals of lead bromide(CH3NH3PbBr3 was grown from DMF solutions dissolved in equimolar ratios of lead bromide and methyl bromide.In order to realize the controlled growth of crystals,the interface growth mechanism was first investigated by AFM.It was found that the growth of the(100)plane of CH3NH3PbBr3 crystals was controlled by two-dimensional nucleation growth at low concentrations,and the step flow growth mode was changed at higher concentrations.Excessive concentrations can cause the CH3NH3PbBr3 crystals to transform into layers.According to the inversion temperature solubility and growth mechanism of CH3NH3PbBr3,two growth methods can be used for the growth of CH3NH3PbBr3 crystals:constant temperature method and temperature increase method.The isothermal method refers to the growth of a solution containing a seed crystal of lead bromide in methylamine at a temperature.The law of warming is to increase the temperature of the lead bromide methylamine solution containing the seeds by gradually increasing the temperature by reverse temperature method.Both methods can obtain large crystals of lead bromide methylamine.The temperature rise method can obtain the perfect cubic block CH3NH3PbBr3 single crystal.At the same time,its crystal structure and optical properties were studied by XRD,UV-Vis absorption spectroscopy,and fluorescence spectroscopy.The single crystal of CH3NH3PbBr3 belongs to a cubic system and its space group is:The unit cell parameters are a=b=c=0.05919 A and the bandgap is 2.10 eV.The results of this study and the discussion of crystal growth methods are directed to the growth of other organic-inorganic hybrid perovskite crystals(eg,lead chloride methylamine,methylgermanium perovskite single crystal,lead-free perovskite,etc.)As well as studying the optoelectronic anisotropy of the hybrid perovskite single crystals,the idea was provided. |
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