Study On Chromatographic Performances Of White Organic Light-emitting Devices Employing DCJTB As Color Conversion Layer

Organic light-emitting device(OLED)is known as the next generation of solid-state lighting and flat displays due to their advantages such as low driving voltage,wide viewing angle,and can be prepared on flexible substrates.In particular,white OLED(WOLED)has attracted wide attention because they can be used as light sources to provide healthy and comfortable lighting,and to be more energy-saving and environmental protection.Although the WOLED technology has been widely used,the high price of product devices and needs to further improve performance,such as device efficiency,stability,and technology maturity have hindered the process of OLED commercialization.Therefore,the WOLED in this thesis was realized by employing the down-conversion structure with a lower cost and simpler preparation process.Meantime,the researches including the FIrpic-based blue phosphorescent OLEDs,the process of color conversion layer(CCL),and the effect of DCJTB on the device performance were implemented,and the details are as follows:1.Research on FIrpic-based blue OLED.First,to explore the effect of the electron transport layer(ETL)on device performance,a series of the FIrpic-based blue light devices with a single-light-emitting layer were prepared.When the material of the ETL is Tm Py PB,and its thickness is 30 nm,a blue OLED with a maximum brightness of 10710 cd·m-2 and a maximum current efficiency of 24.28 cd·A-1 is obtained.Then,the buffer layer near the anode was studied.The recombine region of the excitons can be adjusted by changing the thickness of the buffer layer.When the thickness is 5 nm,the light-emitting region is located in the center of the light-emitting layer,leading to a peak brightness of 9106 cd·m-2 and peak current efficiency of 30.76 cd·A-1,respectively.Finally,a blue light OLED with a double light-emitting layer(D-EML)based on FIrpic was prepared,and the effect of the host material of D-EML blue light on device performance was studied.These results show that the device with the D-EML structure of m CP:FIrpic/TPBi:FIrpic possesses the optimal performance with a peak brightness of 18000 cd·m-2 and peak current efficiency of 36.52 cd·A-1.2.Research on the CCL based on DCJTB.First,the spectra and CIE coordinates of both the FIrpic and DCJTB were studied.This result displays that there is a large overlap between the absorption spectrum of DCJTB and the electroluminescence(EL)spectrum of FIrpic.The emission peak of photoluminescence(PL)spectrum of the DCJTB is around 610 nm,which means that DCJTB can absorb some of the energy from the FIrpic,and emit light with the wavelength of near 610 nm in the PL,which provides a theoretical basis for obtaining WOLEDs by using the FIrpic and DCJTB.Furthermore,the CCL with DCJTB concentrations of 0.5%,0.7%,1.0%,and 1.5% were prepared,which laid the foundation for the next study of the effect of DCJTB concentration changes on device performance.3.The achievement of the WOLED based on the CCL of DCJTB.The WOLED can be obtained by combining D-EML blue light with CCL of different DCJTB concentrations.It is indicated that the device performance can be adjusted by changing the concentration of DCJTB within CCL.As the concentration of DCJTB increases,the color of the device gradually changes from the cyan into white and into the red.When the concentration of DCJTB reaches 1.0%,the device obtained a WOLED near the iso-energy point of white light,with a CRI of 69 and a CIE of(0.33,0.31).In order to further improve the device performance,based on a white light device with a DCJTB concentration of 1.0%,we inserted a structure of TPBi(2 nm)/TPBi:Ir(ppy)3(10 nm)between its electron transport layer and the second light-emitting layer.The study found that the exciton recombination regions can be limited and the absorption spectrum of DCJTB can be expanded by the TPBi(2 nm)/TPBi:Ir(ppy)3(10 nm),realizing the improvement in both the efficiency and color rendering of the WOLED.Its CRI and current efficiency are increased from 69 into 81 and from 13.4 cd?A-1 into 17.8 cd?A-1,respectively.Simultaneously,the CIE of the device only drifted(0.01,0.02)under 1-100 m A?cm-2,which exhibits that the WOLED possesses a good color stability.