黄色磷光和高效蓝色荧光混合的WOLE.ppt

1、Contents,全色显示 固体照明光源 液晶显示的背光源,WOLED,环境友好 超薄 重量轻高的发光效率,结合蓝色荧光和红色或黄色磷光发射体的WOLED应运而生。但由于大多数常见的荧光材料的效率低于磷光材料的。因此，基于高效率荧光的混合WOLED的发展是实现高性能所不可或缺的。,Experimental detail,The WOLEDs were based on blue fluorescent emitter PT-86 (purchased from LumTech Corporation) and yellow phosphorescent emitter PO-01 doped

2、into blue host (PT-05) (from LumTech Corporation) and 4, 4-N, N-dicarbazole-biphenyl (CBP) hosts, respectively. Prior to device fabrication, Indium Tin Oxide (ITO)-coated glass substrates were carefully cleaned by scrubbing and sonication. All devices were fabricated with conventional process. 4,4,4

3、-tris(3-methylphenylphenylamino)-triphenylamine (m-MTDATA) and 7-diphenyl-1,10-phenanthroline (Bphen), served as hole injection layer, and hole-blocking layer (HBL)/electron transporting layer, respectively. Tris(phe-nylpyrazole) Iridium (Ir(ppz)3)was served as hole-transporting layer (HTL) and elec

4、tron-blocking layer (EBL). The thermal deposition rates were 0.1, 0.05 and 0.5 nm/s for organic materials, LiF and Al, respectively. The active area of the devices was 4 mm2.,The EL spectra and CIE coordinates of the devices were measured by a PR650 spectroscan spectrometer, and the current density-

5、voltage (J-V)-luminance characteristics were recorded simultaneously by combining the spectrometer with Keithley 2400 programmable voltagecurrent source. The color rendering index (CRI) values of the devices were calculated with software SETFOS 3.0 fromFLUXIM AG. All measure- ments were carried out

6、at room temperature under ambient conditions.,Results and discussion,An increase in the PT-86 concentration can reduce the hopping distance and subsequently promote the carrier transport in the emission layer (EML), further increasing the current density in the device.,In succession, devices based o

7、n PT-86 and PO-01 combinations were fabricated by utilizing BPhen and Ir(ppz)3 as interlayer and fixing PT-86 doping concentration at 5 wt.%.,For device D1, a relatively larger increase in yellow with respect to the blue emission (ratio of the photons from PO-01 and PT-86 emission: RY/B) is found in

8、 EL spectra at low voltages (6V),while the RY/B is nearly unchanged at higher voltages.,Fig.4.,在低驱动电压下，由于Ir(ppz)3电子阻挡层的存在，电子更多的用于发射蓝光，极少的注入电子可以到达中间的Y-EML，形成发黄光的激子。电压的增加使得更多的电子通过EBL，在Y-EML得到高的电子浓度，导致黄光发射增强，RY/B增加。当电压增加到6V时， Y-EML中多余的电子将转移到B-EML中，与此同时，Y-EML利用空穴。因此，在整个EML层中，载流子/激子达到平衡，最终导致高电压下RY/B 稳定。,

9、It can be noted that the RY/B initially increases and then decreases dramatically with a further increase in applied voltage.,The PO-01 exciton recombination region of device C1, as distinct from device D1, is mainly located at the HTL/Y-EML interface, where there is a much higher exciton density at

10、 the same applied voltage. Thus, device C1 will show a more severe TTA and TPA at high applied voltage, which restricts the enhancement of the yellow emission intensity. Therefore, a decrease in RY/B is observed.,For device C1, the reason for the increase in RY/B at low voltage is the same with that

11、 of device D1. While the decrease in RY/B at higher applied voltage is proved to be the triplettriplet annihilation (TTA) and triplet-polaron annihilation (TPA) of PO-01 exciton. because PO-01 acts as a transporting channel in CBP (see Fig. 4(c).,Fig.4.,Conclusions,We have demonstrated efficient WOLEDs using complementary blue fluorescence and yellow phosphorescence based on different device structures.,The best white device reaches a maximum CE of 24.7cd/A at 1000 cd/m2 with CIE coordinate of (0.44, 0.48).,Devices based on different device architectures ex