一种利用双发光区的有机红光电致发光器件

Realization of Red Organic Light-emitting Diode by Introducing the Double Emitting Zone

针对一般掺杂结构的红光有机电致发光器件效率随外加电压的增加而迅速下降 ,同时色度逐渐变差的特点 ,我们引入了在NPB层和Alq3 层内同时掺杂DCJTB的具有双发光区的器件结构。制备的双发光区掺杂器件在驱动电压 8～ 2 0V内发光效率只下降了 4 % ;而色度从 8V时的 (x =0 .6 2 87,y =0 .36 6 3)变化到 2 0V时的 (x =0 .6 0 75 ,y =0 .384 1) ;器件的发光亮度从 8V时的 178cd/m2 变化到 2 0V时的 5 96 2cd/m2 ,具有较好的性能水平。观察到器件效率基本上不依赖于外加电压的变化而变化的特性 ,同时器件也保持一个比较好的色纯度 。

The red organic LEDs with high brightness and good color purity are necessary for the achievement of full-color emission displays. Commonly, the red OLEDs were made by doping the DCJTB into the Alq_3 host due to its stability and charge-transporting ability. But this doped system showed a contrary phenomenon of low efficiency (at high concentrations of DCJTB) or poor color purity (at low concentrations of DCJTB). Meanwhile, the efficiency of these devices declined rapidly after it reached the maximum efficiency point with the applied voltage increasing. Although intensive research has been made in recent years, the performance of red devices is not satisfactory either the luminance efficiencies or the color purity. In this paper, we fabricated organic EL devices with double emitting zone in order to obtain the efficiency independent on the applied vol-tage and together with good color purity. The saturated red organic light-emitting diode (OLED) has been realized by doping an emitting material in the hole-transporting layer (HTL) and electron-transporting layer (ETL) to form double emitting zone. The red dopant, DCJTB, was doped into the NPB layer and Alq_3 layer, which both act as the emitting layer. The optimal device, with a structure of ITO/CuPc/NPB/NPB∶DCJTB/Alq_3∶DCJTB/Alq_3/ LiF/Al, showed a good performance of the current efficiency being relatively independent of the drive voltage in a wide range from 8 V to 20 V (only reduced by 4%)and the chromaticity coordinates changed from 8 V(x=0.628 7, y=0.366 3)to 20 V(x=0.607 5, y=0.384 1),and the devices maintain a pure red emission. That may be helpful to ameliorate the lifetime of the organic electroluminescence (EL) devices and adjust the gray-scale for the future full-color display panel.