Defect Passivation Of Perovskite Thin Films And Performance Study Of Perovskite LEDs

Organic-inorganic hybrid perovskite materials have excellent photoelectric properties and can be used as active layer materials for electroluminescent devices.It has the advantages of low raw material cost,simple preparation process,adjustable color gamut,high color purity,and strong application potential in display and lighting fields.However,the organic-inorganic hybrid perovskite materials have many disadvantages as the active layer of the thin-film light-emitting device:the recombination efficiency of the carrier in the perovskite layer is low,and the efficiency of the effective injection of the carrier into the perovskite layer is poor.The physical processes and mechanisms associated with complex luminescence have not been fully understood.In this paper,organic-inorganic hybrid perovskite CH₃NH₃PbBr₃ was selected as the research object,and the effects of ionic additives on the morphology,crystallinity,and luminescence properties of perovskite films were studied.The photophysical processes of CH3NH3PbBr3 green LED devices were studied.The main conclusions are as follows:?1?Sodium bromide,an ionic additive,improves perovskite crystallization and the luminescence of the device.An ionic additive sodium bromide?NaBr?was introduced into the CH₃NH₃PbBr₃ perovskite precursor solution to prepare a CH₃NH₃PbBr₃perovskite electroluminescent device based on sodium bromide passivation.The maximum brightness of the device was increased from 1059 Cd/m² to 6942Cd/m²,the maximum current efficiency increases from 0.10 Cd/A to 0.72 Cd/A.Scanning electron microscopy?SEM?and atomic force microscopy?AFM?showed that adding sodium bromide can effectively improve the crystal growth and film coverage of perovskite films.X-ray diffraction?XRD?tests show that sodium bromide can significantly improve the degree of crystallinity of perovskite films.Further,the steady-state photoluminescence?PL?,time-resolved photoluminescence?TRPL?,and electroluminescent?EL?and electrochemical impedance spectroscopy?EIS?measurements of thin films indicate that sodium bromide can effectively passivate the surface defects of the perovskite crystal grains and improve the efficiency and rate of exciton radiation composite in the perovskite active layer,and the performance of the device is significantly improved.?2?The ionic additive benzyl trimethylammonium bromide improves the film formationandluminescencepropertiesofperovskitefilms.Benzyltrimethylammonium bromide with"dual inactivation"of anions and cations was introduced into the CH₃NH₃PbBr₃ perovskite precursor solution to prepare the CH₃NH₃PbBr₃perovskiteelectroluminescentdevicesbasedon benzyltrimethylammonium bromide passivation.For light-emitting devices,the maximum brightness of the device is increased from 4050 Cd/m² to 10821 Cd/m²,and the maximum current efficiency is increased from 0.27 Cd/A to 0.96 Cd/A.SEM,AFM and XRD tests showed that benzyl trimethylammonium bromide increased the coverage and crystallinity of perovskite films more than sodium bromide.PL,EL and EIS tests also proved that the addition of benzyl trimethylammonium bromide can effectively improve the efficiency and rate of carrier radiation in the perovskite layer,and the device efficiency is significantly improved.