Research On The Preparation And Performance Of Per-bromine Perovskite Blue Light-emitting Diode

In recent years,hybrid perovskite materials have sprung up in the field of photovoltaics and optoelectronics,and have become a hot "star material".Perovskite-based light-emitting diodes have attracted people's attention due to their excellent performance.In the past few years,the development of red and green emitting PeLEDs has grown rapidly,and the corresponding external quantum efficiency(EQE)has exceeded 20%.However,the research progress of blue-emitting PeLED still has certain challenges due to its poor material quality and improper device structure.This paper takes the realization of low-dimensional blue perovskite material-based light-emitting diodes as the starting point and goal.By introducing organic long-chain small molecules into the perovskite,the size of the perovskite is reduced,and the dimension of the perovskite is reduced.The anti-solvent is added with organic small molecule polymers to passivate the surface defects of the perovskite,thereby preparing a multi-cation perbromine perovskite film.A series of film forming conditions are optimized for the thin film,and the structure of the device is optimized,and then a high-performance blue perovskite light-emitting diode is prepared.The main research contents of this paper are as follows:Firstly,the film forming conditions and device structure of the PPABr-based perovskite film were optimized.By optimizing the ratio of the perovskite solution,the type of anti-solvent,the timing of adding the anti-solvent,the solution before spinning and the temperature of the substrate,a thin film with a PL spectrum at 485 nm and a large PL peak is obtained to prepare perovskite devices.The optimized results of the film are:the ratio of the perovskite solution is PbBr2:CsBr:RbBr:PPABr=1:0.32:0.96:0.4,the anti-solvent is CF,the temperature of the solution and the substrate is 70?+70?,and the spin coating rate is 1000 r/min,spin coating time is 120 s and anti-solvent is added dropwise after 60 s.Based on the optimized perovskite film,the device structure of the blue PeLED is optimized.Perovskite films based on PPABr have fabricated perovskite devices with two different device structures(IPI structure and PEDOT:PSS structure).Compared with the IPI structure,the PEDOT:PSS structure has better device performance.It achieves a maximum brightness of 1500 cd/m2 at 488 nm,a peak EQE of 1.42%,and a CIE color coordinate of(0.074,0.255).There is no obvious change in the shape of the corresponding EL spectrum under different applied bias voltages,indicating that the device has excellent electroluminescence color stability.Secondly,based on the optimization of PPABr-based perovskite film forming conditions and device structure,the small organic molecule 4,4',4"-tris(N-carbazolyl)triphenylamine(TCTA)was introduced into the anti-solvent chloroform(CF),by optimizing the concentration of doped organic small molecule TCTA,obtains a dense,flat,and uniform perovskite film to prepare high-performance perovskite devices.The introduction of TCTA can effectively improve the photoluminescence quantum yield(PLQY)and fluorescence lifetime of the perovskite film,achieve excellent charge injection,and improve device efficiency.Based on this method,the optimized blue PeLED The maximum brightness at 488nm is 2295 cd/m2,the peak EQE is 1.95%,the emission peak is at 488 nm,the full width at half maximum is 21 nm,and the CIE coordinates are(0.074,0.255).Finally,the perovskite film and its light-emitting diode based on double long chains(PEA and BA)are studied.The introduction of appropriate small organic molecules(poly(9-vinylcarbazole))into the anti-solvent(chloroform)can effectively passivate the surface defects of the film and increase the photoluminescence quantum yield(PLQY)and fluorescence lifetime,achieves excellent charge injection and suppresses non-radiative recombination required for effective blue electroluminescence(EL),thereby improving device efficiency.Based on this scheme,the optimized blue PeLED has excellent device performance.It achieves a maximum brightness of 3136 cd/m2 at 488 nm,a peak EQE of 3.49%,a full width at half maximum of 21 nm,and CIE coordinates of(0.075,0.256).Most importantly,the optimized blue PeLED has excellent color stability,and the shape of the corresponding EL spectrum does not change under high bias or continuous operation.