Heh-Lung Huang

High Energy Gap OLED Host Materials for Green and Blue PHOLED Materials

In this paper, we developed a series of novel arylamino-containing spiro triplet state host materials for green and blue phosphorescent emitters. With high enough energy gap and compatible HOMO, LUMO levels, we demonstrated the green PHOLED with a low driving voltage of 2.5 V and a high power efficiency of 38.5 lm/W. We also demonstrated blue PHOLED with a very low driving voltage of 3.0 V and a current efficiency of 9.2 cd/A.

Interface and thickness tuning for blade coated small-molecule organic light-emitting diodes with high power efficiency

We developed a general method based on fluorescence microscopy to characterize the interface dissolution in multi-layer organic light-emitting diodes (OLEDs) by blade coating. A sharp bi-layer edge was created before blade coating, with the bottom layer being insoluble and top layer soluble. After blade coating, fluorescence images showed that the edge of the top layer shifted when the layer dissolved completely, whereas the bottom layers edge remained in place as a positioning mark. The dissolution depth was determined to be 15–20 nm when the emissive-layer host of 2,6-bis (3-(9H-carbazol-9-yl)phenyl) pyridine (26DCzPPy) was coated on the hole-transport layer of N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine(NPB), which was consistent with a sudden drop in efficiency of orange OLEDs with layer thickness below 20 nm. Thus, the layer thickness of OLEDs was optimized to stay more than 20 nm for blade coating. For a two-color white OLED with the structure TCTA/26DCzPPy:PO-01-TB:FIrpic/TPBI, efficiency was 24 cd/A and 8.5 lm/W at 1000 cd/m2. For a three-color white OLED with Os(fptz)2(dhpm) added as the emitter, the efficiency was 12.3 cd/A and 3.7 lm/W at 1000 cd/m2. For a green device with the structure TCTA/26DCzPPy:Ir(mppy)3/TPBI, the efficiency was 41.9 cd/A and 23.4 lm/W at 1000 cd/m2.

Novel and Efficient electroluminescent organo-iridium phosphorescent OLED materials

We investigated and synthesized different orientation and substituted group of the thieno-pyridine framework organo-iridium complexes ( PO-01, PO-02, PO-03 ). These materials exhibited yellow light. Fabrication of these emissive phosphorescent dopants with the device configuration of ITO/ NPB/ CBP: Ir-complex (4–6%) /BCP/Alq 3 /LiF/Al showed the EL emitting peak from 532nm to 564nm. The electroluminescent efficiencies of the devices were from 9.62 lm/W to 30.41 lm/W and maximum brightness was all above 7000 cd/m 2 . We demonstrated high-efficiency, high-brightness and saturated yellow Ir-complex phosphorescent materials for OLED.

High efficient solution processed yellow phosphorescent iridium emitters

A new small molecular yellow iridium complex was synthesized (PO-01-TB). A solution process OLED prepared using 6% of PO-01-TB as dopant in blend of PVK exhibits yellow emission with current efficiency of 35 cd/A.