Application Of Doped Perovskite Quantum Dots And Interface Modification In LEDs

All inorganic perovskite quantum dots（PQDs）as a kind of semiconductor nanomaterials with excellent properties,own higher than 90%of photoluminescence quantum yield（PLQY）,narrow full width at half-maximum（FWHM）and tunable emission spectrum from ultraviolet to near-infrared.These advantages make PQDs has a broad application prospect on display and lighting field.Preparation of PODs and QLEDs are becoming more and more mature,which performance has made explosive breakthrough,but it is still difficult to meet the practical application requirements.Based on the above research background,this paper aims to improve the material properties and devices efficiency of PQDs,and takes ion doping and interface modification as the solution to design experiments.Finally,ideal results were achieved.（1）Lanthanide with strong spin coupling effect is used to inhibit the deletion of Cl^-,so as to effectively improve the photoelectric properties of materials.DFT calculation shows that lanthanum partially replaces lead,which effectively inhibits the formation of defect states and increases the radiative recombination rate of excitons.By varying temperature fluorescence and spectral fitting,the La³⁺-doped PQDs obtained higher carrier temperature and exciton binding energy.By optimizing the process of hot injection method and using La Cl₃ as the doping ion source,blue PQDs with PLQY of 84.3%were obtained in the range of 443～500 nm under the condition of La³⁺doping amount of 5.43%.In the electroluminescent devices,La³⁺doping is beneficial to suppress the ion migration effect,and the EQE of 2.17 and 3.25%are obtained at 480 and 489 nm,respectively.（2）The blue emission is realized by changing the energy level structure of Cs Pb Br₃ with Zn²⁺doping.PQDs with polar ion shells were prepared by means of low temperature reaction and post-treatment of Br-rich salt solution.At the emission wavelength of 456 nm,the PLQY can reach 98.93%.Subsequently,blue PQDs phosphors were successfully prepared by Si O₂ coating,and green PQDs phosphors with undoped Cs Pb Br₃ were prepared too.Then,a device with warm white emission was prepared by combining KSF red phosphors.In the aspect of electroluminescent devices,the white light devices with single PQDs layer were constructed by combining the characteristics of exciplex emission between PVK and TPBi and Zn²⁺-doped Cs Pb Br₃ PQDs.By adjusting the device structure,the adjustment of cold white and warm white was achieved for the first time.（3）The interface engineering technique is used to modify the hole transport layer by a simple self-assembly method using small diamine molecules.The QD films show enhanced PL intensity and reduced fluorescence quenching properties after modification.In addition,diamine molecules have the function of auxiliary film forming,the pinhole and leakage current of the light-emitting layer can be reduced,and the film smoothness can be enhanced.Finally,the performance and stability of green electroluminescent devices can be effectively improved.The luminance,EQE and T₅₀ at an initial brightness of 1000 cd/m² are 78634 cd/m²,8.90%and 16.8 min,respectively.