Study On Red Perovskite Light-emitting Diodes Based On Additive And Less Lead

Organic-inorganic hybrid perovskite has developed rapidly in recent years due to its advantages of dual-carrier transport,high defect tolerance,easy modification of the structure and simple fabrication process.Light-emitting diodes(LEDs)prepared using perovskite materials as the light-emitting layer have also made continuous breakthroughs in the past five years.Perovskite LEDs have achieved an external quantum efficiency(EQE)of more than 20%in both red and green light emissions,and the efficiency of blue perovskite LED has also reached 12%.However,if it is used as a commercial display screen,there is still a lot of room for improvement.In this thesis,the luminescence performance of red perovskite LED is studied from the two aspects: passivation of perovskite grains with additives to improve the photoelectric properties of perovskites,partial replacement of lead with zinc to reduce the proportion of toxic heavy metal lead.The details are as follows.(1)In order to improve the luminous efficiency of the red perovskite LED,it is particularly important to control the morphology and grain size of the perovskite film.For the first time,ethylamine iodic(EAI)is selected as an organic additive and incorporated into the threedimensional perovskite precursor solution in the thesis.The organic additive EAI can effectively inhibit the growth of large perovskite grains while reducing the density of defect states.The photoluminescence quantum yield(PLQY)of the high-quality perovskite film reached 28%,which was obtained by simple solution processing technology and molecularscale self-assembly technology.Based on this,we obtained a deep red perovskite LED with a turn-on voltage of 2.7 V,an electroluminescence peak of 680 nm,CIE(Commission Internationale de l′Eclairage)coordinate of(0.71,0.28)and a maximum EQE of 7%.Additive engineering can promote the dense growth of perovskite and reduce the grain size,improve the quantum confinement effect,which are conducive to obtaining high-efficiency perovskite LED.(2)In order to develop environment-friendly perovskite materials,it is imperative to reduce the proportion of the toxic element lead while maintaining the photoelectric properties of the perovskite itself.In order to match the valences of the elements,the non-toxic and harmless zinc element,which is abundant in the earth,is selected as a substitute for reducing the toxicity of lead.After systematic testing and characterization,we found that the partial replacement of lead by zinc with a smaller atomic radius in the crystal structure would shrink the perovskite grains,but did not influence the internal structure of the perovskite.In addition,the PLQY of the perovskite film using zinc to partially replace lead reached 45.2%.In the end,we obtained a pure red perovskite LED with an EQE of 9.5%.This is also the highest performance of quasi-2D less-lead red perovskite LEDs currently reported so far.Therefore,the partial replacement of the homovalent element zinc takes into account the structure and photoelectric properties of the perovskite,and provides certain guidance for the development of low-toxic/non-toxic highefficiency perovskite LED.