Research On The Realization And Perspective Of High Color Gamut OLED Devices

In recent years,organic electroluminescent devices,especially top-emitting organic light emitting diodes(OLEDs),have received extensive attention from researchers in lighting and flat panel display applications.However,there are many problems that need to be solved in the top emission OLEDs,such as the implementation of high color gamut devices,the angle dependence of the emission spectrum caused by the microcavity effect,and the problem of luminance attenuation and white field matching of devices.This thesis focuses on high-gamut top-emitting OLEDs to solve these issues.(1)The improvement in the color gamut of the top-emitting OLEDs and their change in luminance and chromaticity with the visual angle were investigated.Top-emission OLEDs with different cathode thicknesses and coupling layer thicknesses were designed,and a single-color device was prepared by vacuum evaporation.The experimental spectral and colorimetric data show that with the thickness of the red coupling layer material of 650 A and the cathode thickness of 180 A,the color CIE x of the device is up to 0.6943.Increasing the thickness of the green coupling layer material to 750 A and the cathode thickness to 200 A,the chromaticity value CIE y of the device reaches a maximum of 0.7391.When the blue coupling layer material has a thickness of 550 A and the cathode thickness is 185 A,the chromaticity CIE y is a minimum of 0.0494.With increasing the thickness of the cathode and the coupling layer,the difference in viewing angle and the decay of the brightness become more and more obvious.The maximum difference in the visual angle of the red light top emitting organic light emitting diode is up to 0.06,and the luminance decays to 30%of the initial value.The green light top emission organic light emitting diode yields the largest visual angle difference of 0.029,and the luminance decays to 20%of the initial value.In terms of the blue light top emission organic light emitting diode,the maximum difference in viewing angle is 0.038 and the luminance decays to 20%of the initial value.(2)The colorimetric optimization of high color organic light-emitting diodes and the change of luminance and chromaticity with the visual angle in high color gamut were investigated.A high color gamut organic light-emitting diode device near the BT 2020 color gamut area was obtained by employing an emissive material with narrow spectrum and optimizing the thicknesses of the cathode and the coupling layer.From the viewing angle and chromaticity data of the high color gamut OLEDs,it is shown that the maximum CIE x value of the red device reaches 0.7028,the maximum CIE y value of the green device is 0.7391,and the minimum CIE y value of the blue device is 0.488.Its chromaticity in the 1976 color gamut system area reached 142.6%of the NTSC standard color gamut area,and 94.9%of high color gamut BT.2020 standard color gamut area.(3)The white field matched with high color and gamut organic light emitting diodes and the change of luminance and chromaticity with the observation angle in the white field were also investigated.By the comparison of the white field brightness and the color cast data under different viewing angles for different chromaticity red,green and blue devices,it is shown that the white field brightness is reduced to 15.9%of the initial value and the viewing angle difference is 0.094.In the low color gamut,the white field brightness is reduced to15.7%of the initial value and the viewing angle difference is 0.081.