Research On Electroluminescent Devices Based On Bule Quantum Dots

Quantum dots are widely used in the development of new-generation light-emitting diodes（LEDs）due to their excellent characteristics such as adjustable emission wavelength,high color purity,high fluorescence efficiency,ease of solution preparation and good stability.Blue emissive quantum dots（QDs）and their LEDs are of great significance to the white-light lighting and RGB full-color display industries.This thesis selects blue carbon dots（CDs）and blue perovskite QDs（Pe QDs）as the research objects,and prepares organic-inorganic hybrid heterojunction（OIHH）electroluminescent devices based on these blue emissive QDs.Electroluminescent properties of the devices have been studied systematically and the results have been achieved as follows:（1）In the process of designing OIHH LEDs based on the blue emissive QDs,ZnO nanowires（NWs）were used as the electron transport layer.ZnO NWs grown hydrothermally had a typical hexagonal wurtzite structure and grew perpendicular to the ITO glass substrate along the（002）preferred crystal plane.The photoluminescence（PL）of ZnO NWs had a smooth broad peak in the visible range centered at 577 nm.In addition,there was also a near-band-edge（NBE）emission in the ultraviolet（UV）region,with the peak position at 379nm.（2）Blue CDs were introduced to regulate the blue light emission of PEDOT:PSS/ZnO NWs OIHH LEDs to realized near-white LEDs.It was found that the blue and green emission peaks at 460（436）and 545（523）nm in the EL（PL）spectra originated from the CDs.A thin layer of PMMA spin-coated between the CDs/ZnO NWs and PEDOT:PSS not only modified the interface of CDs/ZnO NWs and PEDOT:PSS,but also significantly improved the blue light emission from the CDs and ZnO NWs,thus making the emission color of the device tune from yellowish green to near white.Through analysis with the energy band diagram,it was found that the high barrier provided by the PMMA modification layer can effectively prevent the injected electrons from overflowing into the PEDOT:PSS,and allow the electrons and holes to recombine radiatively at the CDs/ZnO NWs side,thus greatly enhancing the blue light of CDs and ZnO NWs to finally shift the device emission color to the near white.（3）Using DDAB as the cosolvent and ligands,high-quality NiCl₂-doped Cs Pb Br₃ QDs were successfully synthesized in air.The results from XRD,EDS,UV-vis,PL and TRPL showed that the quality of Cs Pb Br₃Pe QDs were still high even when bromine ions（lead ions）were successfully replaced by some chloride ions（nickel ions）.With increasing the amount of nickel chloride,the emission color of the Pe QDs was carefully controlled with the emission peaks of NiCl₂-doped Cs Pb Br₃ QDs blue shifted from 515 to 452 nm.On this basis,an OIHH-structured blue electroluminescent device（486 nm）based on Cs Pb_0.7Ni_0.3Br₂Cl₁ QDs was prepared and demonstrated.Our findings provided a feasible way to prepare blue perovskite LEDs.