Synthesis And Exciton Dynamics Of Organic-Inorganic Hybrid Metal Halide Luminescent Materials

In recent years,low-dimensional organic-inorganic hybrid metal halide materials have been widely used in solar cells,light-emitting diodes,photodetectors,photocatalysis and other fields,becoming one of the most popular star materials due to their low temperature solution processability,adjustable energy band structure and excellent photoelectric properties.After thousands of years of change,the field of lighting has evolved to today’s light-emitting diode(LEDs)technology.However,the current white LEDs mainly use "blue light technology" and phosphor to form white light or use a variety of monochromatic light mixed to form white light.On the one hand,a lot of blue light can damage the retina of the human eye.On the other hand,the different phosphors that make up white light will have the problem of spectral instability due to their different lifetimes,which seriously affects the service life of white LEDs in practical applications.Therefore,a single-phase white light material with excellent performance is urgently needed to solve this problem.Based on this background,the work of the first part of this paper reports a series of low dimensional organic-inorganic hybrid lead halide single crystal materials:(BAPP)(PbX4)2 with two-dimensional(2D)structure and(BAPP)PbX6 with zero-dimensional(0D)structure(BAPP=1,4-bis(3-amipropyl)piperazine;X=Cl,Br).All of these single crystal materials exhibit white light emission,especially the(BAPP)PbCl6 single crystal with zero-dimensional(0D)structure,which has the highest white light quantum yield(11.72%).Through a series of characterizations,we show that the white light quantum yield of these white light materials is related to the crystal structure dimension and halogen type.In addition,we further explore the ultrafast optical physical process of the two-dimensional(2D)structure(BAPP)(PbCl4)2 single crystal by using femtosecond transient absorption spectroscopy.This part of work provides a new scheme for the development of single-phase white materials.Although the series of lead based halide materials we synthesized possess white light properties,their white light efficiency is not ideal.In order to obtain better white light performance,we use the common luminous metal element cadmium element instead of lead element strategy to achieve this goal;At the same time,considering that lead and cadmium will inevitably cause toxicity problems in practical applications,which will cause irreversible damage to human body and ecological environment,we further try to replace them with zinc which is the same family element of cadmium,hoping that the materials can not only ensure white light efficiency,but also solve the toxicity problem,so as to realize the application of this series of single crystal in real life.Therefore,the work in the second part of this article is to synthesize four low dimensional organic-inorganic hybrid non-lead metal halide single crystals(BAPP)(CdCl3)4(H2O)2,(BAPP)(CdBr4)2 and(BAPP)(ZnX4)2(BAPP = 1,4-bis(3-aminopropyl)piperazine;X=Cl,Br).In addition to showing better white light performance than lead based materials,these materials also show green long afterglow phenomenon.Interestingly,the afterglow emission lifetime of chlorides is significantly longer than that of bromides,which we attribute to the heavy atom effect of halogens.The detailed photophysical processes of single crystals in this system are studied in detail by means of transient emission spectra,variational temperature fluorescence spectra and femtosecond transient absorption spectra.In addition,we made the QR code images of long-afterglowing chloride single crystal(BAPP)(CdCl3)4(H2O)2 to show its information storage and dual anti-counterfeiting application,indicating the practical application direction of long-afterglowing organic-inorganic hybrid metal halide single crystal materials.