Top emitting white organic light emitting diodes (WOLEDs) hold great promise for high brightness and high resolution active matrix OLED displays. One key challenge of high-performance top emitting WOLEDs is the availability of top electrodes with superior optical, electrical properties. Herein, we demonstrate the application of the dielectric/metal/dielectric structure consisting of a titanium dioxide WO 3 /Ag/WO 3 stack as the transparent top cathode on organic light-emitting diodes (OLEDs). Better performance than that of the normally used semi-transparent Mg:Ag cathode was obtain from the top emitting WOLEDs with the DMD cathode. Moreover, DMD device not only show bright emission similar to that of the IZO cathode device, but also enduring no damage in the device fabrication.
With rapid development toward transparent display, there is an urgent need for electrode with ultra‐high transparency. Here, based on IZO, we propose and experimentally demonstrate a composite cathode capable of efficient micro‐cavity effect within the emitting area and high transmittance in the non‐emitting area. We envision the composite cathode to find its applications in the next generation ultra‐high transparent display technology.
Comparing with traditional single organic light-emitting device (OLED), the luminance efficiency and lifetime of tandem OLED are significantly improved. Therefore, it is of crucial importance to in depth study the influence of microcavity effect on the performance of top emitting tandem OLED. In this paper, taking the blue organic light emitting device for example, the change rule of optical and electrical properties of top-emitting tandem blue-light device are studied by combining optical simulation with practical experiments. The specific experiment is as follows. The top emitting tandem blue organic light devices are fabricated, in which the two light-emitting layers are located at the first anti node and second anti node, the second anti node and third anti node, and the third anti node and fourth anti node in the optical structure of the device respectively. It is found that the performance of the device is better when the two emitting layers of the top-emitting tandem blue light device are located at the second anti node and third anti node in the optical structure of the device respectively. That is to say, when the current density of the device is 15 mA/cm<sup>2</sup>, the current efficiency of the device reaches 10.68 cd/A, color coordinate (CIE<i>x</i>, <i>y</i>) of the device is (0.14, 0.05), and the time of the brightness decreases from 100% to 95% in 1091.55 hours, which is likely to be due to the fact that when the cavity length of the device is long, it can not only improve the recombination rate of hole and electron in the first light-emitting unit, weaken the surface plasmon polarition effect, reduce the influence of the fluctuation of the film thickness on the cavity length of the device, but also play a role of wrapping partials to a certain extent, improve the efficiency and prolong the device lifetime. The research results provide an important theoretical and data basis for designing the top-emitting tandem blue light device with high efficiency and long lifetime. In the future, we will continue to systematically and detailedly study the top emitting tandem organic light-emitting devices, which will provide strong support for preparing the laminated devices with high efficiency long-lifetime, and lower cost.
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