High efficiency yellow organic light emitting diodes with a balanced carrier injection co-host structure

Abstract

We demonstrate herein the design and fabrication of a highly efficient yellow organic light-emitting diode (OLED) with a balanced carrier injection device architecture having a zero electron-injection-barrier host blended with a hole-injection aiding co-host. The resultant yellow OLED showed, at 1000 cd m À2 for example, an efficacy of 59 lm W À1 , current efficiency of 71 cd A À1 and external quantum efficiency (EQE) of 23%, with values of 42 lm W À1 , 47 cd A À1 and 15% EQE without a co-host. The co-host effect that resulted in very balanced carrier injection was also valid for other yellow OLED devices and their efficiency improvement was also very marked. With the use of a micro-lens, the device efficiency is further improved to 79 lm W À1 , 96 cd A À1 and 30% EQE.

High‐Efficiency Orange and Tandem White Organic Light‐Emitting Diodes Using Phosphorescent Dyes with Horizontally Oriented Emitting Dipoles

“…Furthermore, the efficiency roll‐off was low with EQEs of 31.5% at 1000 cd m − 2 and 28.2% at 10 000 cd m − 1 , and a PE of 66 lm W − 1 at 1000 cd m − 2 even without any extra out‐coupling structure. The achieved EQEs of the orange OLED are the highest ones reported up to date . The normalized electroluminescent (EL) spectrum of the device at a current density of 1 mA cm −2 is displayed in Figure e.…”

“…The other way is to utilize both green‐ and red‐emitting phosphorescent materials. The latter method has advantages over the first method in terms of the color‐rendering index and color gamut because of the broad emission spectrum ranging from green to red even though higher efficiencies have been reported using single orange‐emitting dyes …”

Systematical Investigation of Ultrathin Doped Emissive Layer Structure: Achieving Highly Efficient and Long‐Lifetime Orange Organic Light‐Emitting Diodes

“…It implies that bulk doped emitting layer architecture is much more hole dominating and the impact on the electron transport is almost negligible. Accordingly, it can be concluded that the use of the doped ultrathin emissive layer structure may provide excellent electron transport channel and thus balance the carrier flow in the emissive layer, leading to higher efficiencies in device C2 …”

Highly efficient bipolar host material based-on indole and triazine moiety for red phosphorescent light-emitting diodes

“…Therefore, a better carrier recombination within the emitting layer was achieved. [34] Furthermore, the device R1 presented quite better performance, even though the MTZ based single-carrier device shown a more balanced bipolar carrier-transporting ability than that of PTZ. A possible reason was that, generally, the migration rate of hole transport layer (HTL) was higher than that of electron transport layer (ETL) in the devices.…”