F(?)rster Energy Transfer Properties Of Quantum Dot/PDMS Composite Films And Luminescence Properties Of White QLED Devices

With the advantages of good color rendering,high efficiency,and low preparation cost,quantum dot light-emitting diodes(QLED)are expected to become a new lighting technology.Although the performance of QLED devices can initially meet the requirements of commercial applications,the large-area preparation of high-performance white quantum dot light-emitting diodes(WQLED)still faces many difficulties.One of the key bottlenecks that hinder the application of WQLED is the preparation of uniform quantum dot films.Recently,the group has developed a fiber-liquid bridge technology to realize the preparation of large-area preparation of quantum dot films and to construct high-performance large-area QLED devices.However,the existence of severe F(?)rster resonance energy transfer(FRET)in the hybrid quantum dot film seriously affects the device’s performance.The introduction of corresponding polymer materials to suppress the F(?)rster energy transfer process between quantum dot of different colors and effectively enhance the stability of white light devices is of great significance for developing efficient QLED white light illumination technology.In this thesis,PDMS was introduced into an n-octane quantum dot solution to improve the stability of quantum dot films by using the interaction between PDMS and quantum dot,and then effectively suppresses the F(?)rster energy transfer process between quantum dot films of different colors.The effect of the PDMS addition ratio on the structure of quantum dot films prepared by the liquid bridge method was investigated,and large-area uniform quantum dot/PDMS composite films were obtained.On this basis,the F(?)rster energy transfer between the multicolor quantum dot layers in the composite thin film device and its effect on the device performance was investigated,and it was found that the composite thin film did effectively suppress the F(?)rster energy transfer and had a significant effect on the starting voltage and color stability of the white light device.It provides a new approach to realize the construction of highly stable white QLED devices.The specific research contents are as follows:(1)Firstly,the effects of PDMS polymer addition to quantum dot solution on quantum dot dispersion performance were investigated;the modulation effects of PDMS addition in n-octane quantum dot solvent and liquid bridge printing rate on the composite quantum dot film structure were analyzed,and the preparation of large-area QD/PDMS composite film structure was realized;the effects of PDMS addition on QLED device electrical,brightening voltage and luminance were explored.The surface of the PDMS-QD composite quantum dot film is relatively flat with an average roughness of 0.932 nm when the liquid bridge printing rate is 3000μm/s and the PDMS addition is 2.5 wt%,does not affect the brightness voltage of QLED devices.(2)The modulating effect of the ratio of three primary colors of quantum dot on the luminescence color of the composite quantum dot solution and thin film was investigated.When the solvent volume ratio of red,green and blue quantum dot was 1:2:6,the International Commission on Illumination(CIE)coordinates of the hybrid quantum dot devices were(0.33,0.33),where the concentrations of red,green and blue quantum dot were 5 mg/m L,18 mg/m L and 18 mg/m L,respectively;The modulation of the luminescence color of the mixed quantum dot solution,composite quantum dot film and white QLED device by the content of PDMS in the optimal white ratio of mixed quantum dot solution was investigated,in which the addition of 2.5 wt%PDMS in the mixed quantum dot solution can effectively improve the quantum dot yield of the mixed quantum dot solution;the steady-state transient fluorescence spectra were used to test the QD/PDMS composite film The effect of PDMS on the luminescence performance of white QLED devices of hybrid quantum dot films was analyzed,and stable white QLED devices with a start-up voltage of 4 V and CIE coordinates of(0.33,0.32)were obtained;the results showed that the FRET between G/B-QD/PDMS and R-QD/PDMS composite quantum dot films was effectively suppressed.The effect of stacking order of G/B-QD/PDMS and R-QD/PDMS composite quantum dot films on the performance of white QLED devices was investigated,and WQLED devices with maximum brightness and external quantum efficiency(EQE)of162,600 cd/m~2 and 6.07%,respectively,were constructed,and white QLED devices with 1.5 cm×1.5 cm emitting area were prepared based on fiber-liquid bridge printing.