Study On The Optical Property Regulation And Application Of Rare Earth Ions Doped Lead Halide Perovskite Nanocrystals

All-inorganic lead halide perovskite nanocrystals（PeNCs）:CsPbX₃（X=Cl,Br,I）have attracted the wide attention due to their large absorption cross-sections,narrow photoluminescence line width,high photoluminescence quantum yield（PLQY）,and tunable luminescence over entire visible spectral region by halide composition,which have once become a hot material in the field of photoelectric materials and devices.However,the disadvantages of PeNCs,such as the poor lattice stability and limited spectrum in visible region,which limit their practical applications seriously.The rich transition energy levels and 4f electron transition characteristics of rare earth（RE）ions make their emission positions cover the spectral range from UV to NIR.The doping of RE ions into PeNCs can not only improve and expand perovskite with excellent optical properties,such as improving the PLQY of PeNCs,enhancing the stability,but also expand the PL to the NIR or even mid infrared region,which can solve the key problems of PeNCs for practical applications.Up to now,a variety of RE ions have been successfully doped into the lattice of PeNCs.Through the energy transfer from the perovskite host to RE ions,the PL of RE ions has been successfully obtained.However,the defects of perovskite hosts and the low energy transfer efficiency hinder the contribution of RE ions to PL,resulting in the limited application of RE ion-doped PeNCs.For example,the electroluminescence of RE ions in perovskite system has not been realized in the early stage of this paper.In view of this,in this paper,we have conducted a series of studies on how to achieve efficient RE ion-luminescence in all-inorganic Pe NC systems,and device explorations have been carried out for the corresponding material characteristics.The specific work contents are below:（1）We improved the traditional hot-injection method for synthesizing the RE ions doped CsPbX₃ PeNCs.Achieved Sm³⁺doped CsPbCl₃ perovskite with a PLQY of up to 85%.Based on the PeNCs with different Sm³⁺ion-doping concentrations,inverse Pe LEDs were prepared.The device structure is ITO/ZnO/PEI/CsPbCl₃:Sm³⁺/TCTA/MoO₃/Au,demonstrated tunable EL from blue to orange spectrum region,which is the first time to observe the EL of RE ions in perovskite system.More importantly,we achieved the single-component white LEDs with a chromaticity coordinate（CIE）of（0.32,0.31）,a maximum luminescence of 938 cd cm^-2,external quantum efficiency（EQE）of 1.2%,and a color rendering index（CRI）of 93.（2）A method of preparing efficient rare earth(RE³⁺)ions doped Pe NC thin films was reported.First,the band engineering was used for improving the energy transfer efficiency from exciton to RE³⁺ions.Afterwards,the multi-functional additive creatine phosphate（CP）was introduced to the RE³⁺doped PeNCs for post-treatment.Consequently,the white LED based on Eu³⁺ions doped PeNCs shows a peak luminance of 1678 cd m^-2 and a maximum EQE of 5.4%.Furthermore,the band engineering and defect passivation method was also generalized to some other RE³⁺ions doped perovskite LEDs and successfully obtained improved EL.（3）We have prepared two-dimensional（2D）all-inorganic CsPbCl₃ perovskite nanosheets（NSs）doped with RE ions(Yb³⁺)by adjusting the ratio of short chain octylamine（OLAm）in the precursor and the hot-injection temperature.Moreover,Yb³⁺doped CsPbCl Br₂ 2D perovskite NSs were obtained by anion exchange method,and the PLQY was 128%,which realized the quantum cutting in 2D perovskite NSs.Furthermore,we have prepared photodetectors using lateral assembled NSs as the active layers,showing high responsivity and dual-band（UV and NIR）detection capability.The detectivity at 440 nm and 980 nm are 5×10¹² Jones and 2.15×10⁹ Jones,respectively.Finally,based on the power supply system of the perovskite solar cells,the imaging system and the data analysis system of the photodetector array,we realize the visual photoelectric detection,which can collect the detection signal and display the image through the photodetector array.（4）In the synthesis process of Mn²⁺ions doped CsPbCl₃ perovskite quantum dots（PQDs）,long chain ammonium ligand,dodecyl dimethylammonium chloride（abbreviation:DDAC）was incorporated.The incorporation of DDAC will replace ligands of QDs,and will enhance the PLQY and stability of the doped PQDs as well.The PLQY of prepared PQDs was 91%.We applied the improved Mn²⁺ions doped PQDs on the silicon solar cells（SSCs）as the photon converters.The photoelectric conversion efficiency（PCE）increased from 19.64%to 20.65%in SSCs,with a 5.14%increase.