Study On Fabrication Of Stabilized Red Perovskite Quantum Dots And Their Luminescent Performance

Among the numerous emerging display materials,all-inorganic lead halide chalcogenide quantum dots(CsPbX3,X=Cl,Br,I)are attracting attention due to their advantages of high quantum yield(nearly 100%PLQY),narrow half-peak width,high defect tolerance and long carrier lifetime.However,due to the ionic structure and large surface energy of CsPbX3 quantum dots,they are highly susceptible to phase transition and even decomposition under the action of moisture,oxygen,radiation and heating,etc.This certainly limited the subsequent industrial implementation.In this paper,to address the problems of poor stability and device performance of red CsPbX3 quantum dots,we have prepared red CsPbX3 quantum dots with high luminescent efficiency and stability by surface ligand coating and ion doping,and prepared highly effective quantum dots light-emitting devices.The contents are as follows:(1)Improved stability of CsPb(Br/I)3 quantum dots by organosilane coating.The stability of the CsPb(Br/I)3 quantum dots was enhanced by the generation of a protective layer of dense silica on the surface of the quantum dots through the reaction of organosilane with traces of moisture in the air.In addition,organosilane-coated CsPb(Br/I)3 quantum dots were combined with polydimethylsiloxane(PDMS)to produce highly efficient and homogeneous red light-emitting quantum dot films,which have been used to produce LCD backlights.(2)Enhancing CsPbI3 quantum dot stability and device performance via La doping.By introducing small-sized La ions to partially replace the Pb ions,the structural distortion is suppressed and the formation energy of CsPbI3 quantum dots is increased,which fundamentally improves the stability of the quantum dots to environmental,thermal and UV radiation.At the same time,the strong interaction between La ions and I ions,thus effectively suppressing the trap state,promotes the radiation recombination and enables the photoluminescence quantum yield(PLQY)of CsPbI3 quantum dots to achieve 99.3%.The excellent photoelectronic properties of the lanthanum-doped CsPbI3 quantum dots have led to a dramatic improvement in the performance of the PeLEDs,with a five-fold increase in external quantum efficiency(EQE)from 1.19 to 6.01%.(3)Further preparation of highly effective quantum dots and light emitting devices using 3-fluorophenylethylammonium bromide(m-F-PEABr)modified La-doped CsPbI3 quantum dots.Through the anion exchange of Br and I ions,the luminescence peak of the quantum dot film was shifted from the original 687 nm deep red emission of the La-CsPbI3 quantum dot to 663 nm.At the same time,the isopropyl alcohol was used to remove the excess ligands from the quantum dot surface,thereby improving the film formation quality and carrier transport capacity of the quantum dots.The turn-on voltage of the anion exchanged PeLEDs was significantly reduced,and the maximum EQE was increased from 5.69%to 7.39%.