Preparation And Optical Properties Study Of CsPbBr₃ Quantum Dots With High Brightness And Stability

Perovskite quantum dots(Pe QDs)have attracted widespread attention from researchers due to their ultrahigh photoluminescence(PL)quantum yield(QY),wide color gamut coverage,high defect tolerance,and high luminous purity.It is considered as one of the most promising materials for the next generation of display technology Micro-LED.With the research of scholars,the stability of Pe QDs has been exposed a lot of shortcomings.The main drawback of Cs Pb X₃ Pe QDs is the poor chemical stability under ambient conditions.Cs Pb X₃ Pe QDs are sensitive to moisture,light,and temperature due to their low formation energy.Besides,the highly ionic internal bonding results in the ease of ion-exchange reactions and decomposition.To date,the stability of Cs Pb X₃ Pe QDs is still an urgent scientific problem to be solved,and it is also the key to restricting the application of perovskite-based light-emitting devices.To address this key scientific question,this paper starts from isolating the CsPbBr₃ Pe QDs from the external environment and improving their internal structure by growing CsPbBr₃ Pe QDs in situ in mesoporous silica pore channels(SBA-15)and doping the internal structure of the CsPbBr₃ Pe QDs with ions.A dual protection strategy of encapsulation and doping was used to enhance the stability of CsPbBr₃ quantum dots.The study consists of three main parts:(1)Cubic CsPbBr₃ Pe QDs with an average particle size of 9.6 nm,uniform size and regular morphology were prepared by hot injection method at 180?.The CsPbBr₃Pe QDs emit bright green fluorescence under a UV lamp with a wavelength of 365 nm,the emission peak is located at 530 nm,the full width at half-maximum(FWHM)is 22nm,and the photoluminescence quantum yields(PLQY)is 21%.On this basis,we prepared Cs Pb Cl₃ and Cs Pb I₃ quantum dots by the same method and controlled the halide ions in the quantum dots through anion exchange reaction,and then realized Cs Pb X₃(X=Cl,Br,I)Pe QDs emission from 400 nm to 690 nm.(2)The mesoporous silica pore channels were used as microreactors for the in-situ growth of CsPbBr₃ Pe QDs in the pore channels by the hot injection method.In the TEM images and X-ray diffractograms of the resulting composite samples,it can be observed that the quantum dots are uniformly grown in the SBA-15 pore channels with complete structure and good crystallinity without obvious agglomeration.When the molar ratio of Pb Br₂ and SBA-15 in the raw material was adjusted to 1:13,the resulting CsPbBr₃@SBA-15 composite sample possessed good luminescence and the solid PLQY was increased from 21%to 80%.The mesoporous silica shell successfully prevented the contact between the quantum dots and the external environment,and the stability of the composite sample was significantly improved.With heating up,the CsPbBr₃/SBA-15 preserve 72%of its original PL intensity at 80°C and still emit lights even at 120°C.After the sample is placed in a high humidity environment for 12 hours,the PL intensity decreases slightly.Exposing to the ultraviolet lamp for 72 h,the CsPbBr₃/SBA-15 maintain 86%of its original PL intensity.After mixing the composite samples containing different halogens,even for 30 min,there are no spectral shifts occurring and the PL intensity of two emission peaks almost unchanged.A white LED with a wide color gamut of 129%NSTC and a color rendering index of 83 was packaged with a blue chip,commercial red phosphor KSF and CsPbBr₃@SBA-15 composite samples.(3)The Sr²⁺ion-doped CsPbBr₃ Pe QDs were prepared in SBA-15 channels at180°C by hot injection.Compared with the undoped composite sample,the Sr²⁺:CsPbBr₃@SBA-15 sample exhibits more excellent photothermal stability.The fluorescence intensity decreases to 46%of the initial intensity when the temperature is increased to 120°C.The fluorescence intensity of the composite sample retains 96%of the initial intensity after irradiation under UV lamp for 72 h.The enhanced stability of the Sr2⁺:CsPbBr₃@SBA-15 composite sample is attributed to the stabilization of the quantum dot crystal structure by Sr²⁺doping and the isolation of the external environment by the mesoporous silica pores.