Study On Narrow Linewidth Colloidal Quantum Dot Electroluminescent Device

Colloidal quantum dots are widely used in quantum dot light-emitting devices due to their solution processability,high fluorescence quantum yield and high color purity,and are considered to be the most competitive material in the future high-definition flat panel display field due to their wide color rendering range and high color purity of electroluminescent(EL)devices.In recent years,the commercialization of quantum dot flat panel display has been progressing steadily,but at present,quantum dots are mainly used as phosphors for display backlight to achieve a wider color gamut adjustment and enhance the display effect.In recent years,colloidal quantum dot electroluminescent devices(QLED)have made rapid progress and have been given high expectations in the display field.To further enhance color purity,the introduction of microcavity structures is an important implementation strategy to achieve narrower linewidth QLEDs.However,there are still some problems in the field of narrow linewidth QLEDs,on the one hand,the understanding of QLED luminescence mechanism needs to be further deepened,on the other hand,the problem of combining narrow linewidth and high EL efficiency of QLEDs also needs to be solved.On the other hand,the problem of combining narrow linewidth and high EL efficiency of QLEDs is still to be solved.Based on this,this thesis focuses on narrow linewidth QLEDs,introduces optical microcavities into QLED devices,achieves narrower linewidth EL and improves the optical coupling output efficiency of QLEDs through the modulation of photonic density of states by microcavities.On this basis,the first QLED structure with side emission was designed and developed to obtain narrow linewidth polarized electroluminescence with side emission,and the internal mechanism was analyzed.The main work and research results of this thesis are as follows:(1)In the conventional QLED preparation and EL performance study,we synthesized Zn O NPs with smaller particle size and lower surface roughness,further refined the device structure,optimized the solution deposition rate of the light-emitting layer and electron transport layer,and achieved a significant increase in current efficiency(CE)and external quantum efficiency(EQE)compared with the unoptimized QLED device,and the final CE and The CE and EQE of the final device were 63.3 cd/A and 14.92 %,respectively.(2)A narrow linewidth high-performance QLED based on the Tamm microcavity structure was designed and fabricated to achieve an exponential increase in EQE and CE based on narrowing the full width of the EL half height of the QLED.A maximum current efficiency of 92 cd/A and a maximum EQE of 20 % were achieved in the device,and a narrow EL linewidth of about 2.5 times and a narrow PL linewidth of about 3.7 times were achieved at a UV laser pumping energy of 1133 n J compared to the conventional QLED devices prepared under the same conditions.(3)For the first time,QLEDs with narrow linewidth edge-emitting structures were designed and realized photoluminescence with a FWHM of 5.51 nm under UV laser excitation of 1065 n J and electroluminescence with a FWHM of 5.6 nm driven by a current density of 38 m A/cm~2.