High-efficiency and low-voltage p-i-n electrophosphorescent organic light-emitting diodes with double-emission layers

Abstract

We demonstrate high-efficiency organic light-emitting diodes by incorporating a double-emission layer (D-EML) into p-i-n-type cell architecture. The D-EML is comprised of two layers with ambipolar transport characteristics, both doped with the green phosphorescent dye tris(phenylpyridine)iridium. The D-EML system of two bipolar layers leads to an expansion of the exciton generation region. Due to its self-balancing character, accumulation of charge carriers at the outer interfaces is avoided. Thus, a power efficiency of approximately 77 lm∕W and an external quantum efficiency of 19.3% are achieved at 100cd∕m2 with an operating voltage of only 2.65 V. More importantly, the efficiency decays only weakly with increasing brightness, and a power efficiency of 50 lm∕W is still obtained even at 4000cd∕m2.

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

“…3a,b, Supplementary Table 1). These efficiencies are considerably higher than those of the PVK based device and the best polymer light-emitting diodes ever reported in the literature 11 and even comparable with those of evaporated multilayer OLEDs 31 . We also note that there is no perceivable change in luminance as a function of viewing angle (Lambertian factor: 1.03), eliminating the possibility of overestimating the efficiencies.…”

Highly simplified small molecular phosphorescent organic light emitting devices with a solution-processed single layer

“…[1][2][3][4] Highly efficient PHOLEDs with many different organic layers for charge transport and exciton confinement have been realized and commonly fabricated using a conventional vacuum sublimation technique. [5][6][7] Despite highly efficient for these multi-layer PHOLEDs, their application is still limited by a complex fabrication process due to unavoidable high vacuum conditions. The solution-processed means for fabrication of OLEDs using soluble materials would be simple and opens up a pathway toward large area, low cost and high efficiency OLEDs in the future.…”

High efficiency phosphorescent organic light-emitting diodes using carbazole-type triplet exciton blocking layer

“…Other than these, a double EML structure was used and high quantum efficiency of 19.3% was reported. 2,6 A graded doping structure was studied by our group and it also gave a long lifetime as well as high power efficiency. 7 In this work, we studied the use of ͑4,4Ј-N , NЈ-dicarbazole͒biphenyl ͑CBP͒ and N , NЈ-dicarbazolyl-3,5-benzene ͑mCP͒ as an EBL to get high efficiency in green PHOLEDs.…”

“…1 and high power efficiency of 77 lm/ W was reported in PHOLEDs. 2 There have been many studies about light emission and high efficiency in PHOLEDs. [3][4][5][6][7] Many different device architectures were tried to improve the light-emitting efficiency of PHOLEDs.…”