Phosphorescent OLED device

As discussed in Section 7.1, NPB Alq devices may not be representative of many different OLED device structures. It is therefore natural to ask whether the role deep traps play in operational degradation is unique for the NPB Alq devices. To answer this question, we examined a diverse set of fluorescent and phosphorescent OLED devices spanning more than two orders of magnitude difference in stability. The results are summarized in Table 7.1 and the following is noteworthy. Despite the structural and functional dissimilarities in the experimental set, the operation-induced accumulation of fixed positive charge densities and correlation with luminance loss were invariably observed. Although we observed some nonlinearity in luminance-charge... 

The luminous efficiency of OLEDs can be improved Imther by use of phosphorescent emissive materials. Incorporated into OLED devices starting in the 1990s, phosphorescent dopants have a potential to achieve 100% internal quantum efficiency. We will describe materials and architecture developments of phosphorescent OLED devices in Section 14.4. Finally, we discuss the future outlook of the OLED technology in Section 14.5. 

Brief Introduction to Emission Mechanism in Phosphorescent OLED Devices... 

EQE as a function of current density for green phosphorescent OLED devices with mixed EML and various ETLs (see legend). Organic layers NPB (95nm) TCTA (10nm) TPBI+30%TCTA + 6%Ir(ppy)3 (35 nm) ETLs. Anode and cathode are always ITO CF and liF Al. CIE coordinates are all in the ranges (0.296-0.308,0.625-0.634). 

Current density as a function of voltage for green phosphorescent OLED devices with mixed EML and various ETL (see legend). For organic layer structures see Figure 14.45 captions. 

Schematic of white phosphorescent OLED device with six organic materials. (Reproduced from D Andrade, B. et at, SID Inti. Symp. Dig. Tech. Papers, 39, 940,2008. With permission.)...

Kondakova, M. E., Deaton, J. C., Kondakov, D. Y. et al. 2007. High-efficiency low-voltage phosphorescent OLED devices with mixed host. SID Inti. Symp. Dig. Tech. Papers 38 837. 

Ren, X., Tyan,Y.-S., Madaras, M. et al. 2008. High-efficiency long-lifetime phosphorescent OLED devices based on electron-trapping iridium(III) complexes. SID Inti. Symp. Dig. Tech. Papers 39 864. 

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