| Organic light-emitting device?OLED?has a lot of advantages,such as wide material selection,low operating voltage and wide viewing angle.It can be fabricated on large-area flexible substrate,which has aroused widespread interest.White OLED?WOLED?has a wider luminescence spectrum than inorganic light-emitting device?LED?.A WOLED with a high color rendering index?CRI?can provide a healthy and comfortable environment.At present,a tandem WOLED with good color characteristics,great efficiencies and simple preparation process are remains to be developed.In this paper,high-performance tandem WOLEDs are prepared.The content of the paper is mainly divided into the following aspects:1.A blue-yellow complementary tandem WOLED was prepared by using the charge generating layer?CGL?Liq/Al/HAT-CN.By comparing the luminescence spectra,working voltages and brightness of different tandem two-color devices at the same current densities,the charge generation and injection process in CGL was clarified.The operating voltages and brightness of tandem WOLED as well as the blue and yellow single-unit devices were compared at a current density of 10 mA/cm2 and20 mA/cm2,demonstrating the effectiveness of CGL.When the current density was240 mA/cm2,the tandem WOLED achieved a maximum brightness of 11420 cd/m2.Luminescence spectrum of the device is stable.When driving current density is increased from 10 mA/cm2 to 30 mA/cm2,the blue component ratio is only increased by 5%.For the weak microcavity effect existing in the tandem device,we have conducted in-depth research through optical simulation calculation according to the microcavity theory.2.A highly efficient and stable tandem warm white OLED was realized by a simple CGL of CsN3/Al/HAT-CN connecting a fluorescent blue light unit and a phosphorescent red-green two-color unit.The good color stability in red-green two-color devices and working mechanism of efficient CGL were analyzed.When the driving current density is increased from 2 mA/cm2 to 34 mA/cm2,the Ra is over 85and R9 is approximately 57.Duv ensures the validity and rationality of Ra and R9.The tandem warm white OLED has optimum efficiencies of 38.0 cd/A and 22.9 lm/W.It maintains high efficiencies of 35.5 cd/A and 17.2 lm/W at luminance of 1000 cd/m2.3.A highly efficient warm white OLED with multiple light-emitting layers was realized by precisely limiting the exciton recombination region and making full use of the energy transfer between excitons.The maximum efficiencies of warm white OLEDs are 21.4 cd/A and 25.8 lm/W.As the operating current density increases from10 mA/cm2 to 60 mA/cm2,the CIE coordinates change only by?0.004,0.007?,while Ra remains at around 80,and R9 is higher than 20.Duv satisfies the standard of CRI measurement.The color gamut area index GAI is among 90 to 100,which satisfies the requirements of high-quality light source.Finally,the reasons for spectral stability were analyzed. |
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