Dual n-type units including pyridine and diphenylphosphine oxide: effective design strategy of host materials for high-performance organic light-emitting diodes

Abstract

The direct linking of dual n-type units is developed to design novel host materials for improved performance of blue and green phosphorescent organic light-emitting diodes.

Molecular Engineering of Host Materials for High‐Performance Phosphorescent OLEDs: Zig‐Zag Conformation with 3D Gridding Packing Mode Facilitating Charge Balance and Quench Suppression

“…It is interesting that m ‐BPySCz possesses smallest molecular weight and the lowest amorphous stability ( T g = 61.3 °C) among these four analogs, but exhibited best performance in FIrpic PhOLEDs with highest efficiency and lowest efficiency roll‐off, even superior to most of the bipolar host materials reported in literatures . We suppose that, in the case of m ‐BPySCz, the packing mode of host molecules in bulky film becomes the predominating factor to determine the overall performance of PhOLEDs.…”

“…Inspiringly, the m ‐BPyDCz‐hosted B1 also achieved a good performance of 25.0% (2.8 V, 46.2 cd A −1 , 36.3 lm W −1 ) (Figure S10, Supporting Information). In recent years, high efficiencies have been achieved for FIrpic‐based PhOLEDs using a single host which stand for the typical data for blue devices so far, such as Ma, Lee, Li and Wong have respectively reported the efficiencies of 27.5% (49.4 cd A −1 ), 31.4% (53.1 cd A −1 ), 25.3% (55.6 cd A −1 ), and 26.4% (57.6 cd A −1 ). It is obvious that the efficiencies 27.3% (50.3 cd A −1 ) of m ‐BPySCz‐hosted B3 are close to the best data ever reported for FIrpic‐based PhOLEDs.…”

“…Apparently the performance of m ‐BPyDCz and m ‐BPySCz are not only superior to their para ‐linked isomers, their efficiency roll‐off are also comparable with or much lower than those of FIrpic PhOLEDs containing a single host material reported in recent 10 years. Except only a few reports with efficiency roll‐off below 8.0%,[2a,15,17,19,23] most of the FIrpic devices exhibited efficiency roll‐off values in the range of 10–30% or even higher, as summarized in Table S2 in the Supporting Information.…”

De novodesign of D–σ–A molecules as universal hosts for monochrome and white phosphorescent organic light-emitting diodes

“…4 and Table 2, the maximum EQEs for devices B1 and B2 are 29.4% and 21.2%, respectively. Note that device B1 retains a high EQE of 28.2% and a power efficiency (PE) of 48.6 lm W –1 at a luminance of 1000 cd m –2 , proving to be one of the most efficient FIrpic-based devices 16,39–42. By contrast, device B2 shows serious efficiency roll-off at luminance higher than 1000 cd m –2 .…”

Versatile Host Materials for Highly‐Efficient Green, Red Phosphorescent and White Organic Light‐Emitting Diodes

“…[12] In addition, efficient host molecules should also have a high triplet exited state energy (E T ) to achieve efficient energy transfer from the host to the doped emitter [13] as well as appropriate HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels to match the energy levels of the hole and electron transport layers to reduce the driving voltages of devices. [14,15] Indo[3,2,1-jk]carbazole(ICz) is always treated as an electronaccepting group, because the nonbonding electrons in the nitrogen atom are shared by three aromatic units in ICz, indicating that the total electron density would be less in the ICz unit than that in other indolocarzole units. [16] Besides, because of the direct connection of the benzene rings, ICz is a moiety with a totally rigid plane, which is conducive to improving the luminous efficiency.…”