Trapping phosphorescence devices

Polymer light-emitting devices (PLEDs) have attracted considerable interest because of their potential use in portable electronic devices. PLEDs have improved the performance of devices by increasing the device stability and efficiency. Chang and coworkers fabricated an efficient PLED using [Ir(acac)(dbq)2] as the phosphorescent dopant of a pvk matrix layer and bbpo as the electron transport material. Trapping of charge carriers at the [Ir(acac)(dbq)2] dopant sites dominates the EL of the device. This is the first PLED that emits red electrophosphorescence centered at 610 nm, exclusively from the dopant and an EL efficiency of 8.5 cdA (luminance 1287 cdm ) biased at 14.5 mAcm . ... 

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... 

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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