Integration Of Environmental Friendly Perovskites For High Efficiency White Light-emitting Diodes

Perovskite has been widely used in solar cells,photodetectors and light-emitting diodes(LEDs)due to its excellent luminescence properties.Perovskite LEDs have been developed rapidly in recent years.However,with the deepening of the research,many problems restricting the development of LED applications have followed one after another.The first is stability.For example,red perovskite quantum dots usually contain iodine(I)and are not stable under continuous light.The second is the mixing of perovskites with different halogen source,where a very fast exchange reaction between the anions will occur and the visible fluorescence will change rapidly,which will limit their application in LEDs.The final problem is that perovskite materials contain toxic element lead,which will cause great harm to the environment and human health.The above problems are not conducive to the preparation of high-quality white light-emitting diode(WLED)devices.Aiming at the above problems,this paper analyzes the characteristics of environmental friendly perovskite materials from the perspective of material synthesis,device design and preparation,and puts forward corresponding solutions,so as to produce high-quality WLED.The main contents of the paper are as follows:(1)Studies have found that doping metallic elements can reduce the use of lead.The idea of doping perovskite materials was proposed.Less toxic Mn doped Cs Pb Cl₃quantum dots(QDs)with orange light emission and non-toxic Bi doped Cs₂Sn Cl₆with blue light emission were designed and optimized by thermal injection method.Experimenntal analysis shows that both perovskite materials exhibit good stability and can be excited by ultraviolet light.Under ultraviolet light,they show high quantum yield(QY)and wide emission spectrum,which are very conducive for forming continuous spectrum and obtaining white light.They also contain the same anion Cl,thus avoiding the anion exchange reaction during the mixing process.Based on all the high quality characteristics of the above two materials,high quality WLED made from combining of the two materials and a UV LED was optimized and prepared,and the stability of the device was systematically analyzed.(2)Bismuth(Bi³⁺),terbium(Tb³⁺)and antimony(Sb³⁺)were introduced into the matrix material Cs₂Sn Cl₆,and for the first time,two white luminescent inorganic perovskite materials Bi_0.05Tb_1.8Sb₁and Bi_0.05Tb_1.8Sb_0.8doped Cs₂Sn Cl₆were designed and synthesized by solvent thermal synthesis method.Through energy dispersive X-ray spectroscopy,X-ray diffraction,luminescence spectrum,absorption spectrum and luminescence life test,the properties of the two materials were systematically studied.It was found that the two materials showed good stability.In addition,both materials do not contain the toxic element lead,which solves the lead poisoning problem that has been a long-time concern.Two environmental friendly WLED₁and WLED₂with different color temperatures were developed by combining a 380nm UV-LED.The color coordinates are(0.388,0.310)and(0,333,0.268).The stability analysis shows that the devices have very good stability.After 400 hours of continuous operation,the luminous intensity decreases by less than 10%.