Orthogonally Substituted Benzimidazole-Carbazole Benzene As Universal Hosts for Phosphorescent Organic Light-Emitting Diodes

Abstract

The novel ambipolar hosts of o-CbzBz and o-DiCbzBz contain carbazole and benzimidazole through an ortho-connection. The orthogonal conformations cause the triplet state to be confined at the carbazole units to secure efficient energy transfer. The phosphorescent organic light-emitting diodes (PhOLEDs) show a high current efficiency, power efficiency, and low efficiency roll-off. o-DiCbzBz can be used as a host for sky-blue, green, and orange-red PhOLEDs, giving 57.5, 78.4, and 60.3 cd/A, respectively.

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

“…S3†). The two materials show much less redshifts (<15 nm) compared with those (> 50 nm) of BI integrated BCz35 or TPA36 D–π–A molecules in the literature. This further suggests that ICT is efficiently suppressed by virtue of the D–σ–A configuration.…”

9H‐Quinolino[3,2,1‐k]phenothiazine: A New Electron‐Rich Fragment for Organic Electronics

“…[4] In addition to its high thermal/morphological stabilitya nd its high triplet energy (E T ), an ideal host should also possess ab ipolar character,w ith HOMO and LUMO energy levels adapted to the Fermi levels of the electrodes. [6][7][8][9] However,t here is ac ertaina ntinomy between ah igh E T (essential to insure efficient energy transfers) and as hort HOMO/LUMO gap (essential to insure efficient charge injection) and the best trade-off should be found for the ideal host. If the nature of the linkage [10] between the electron-rich and the electron-poor units is of key importance to control the E T as well as the HOMO/LUMO gap, their intrinsic properties remainn everthelesst he most important characteristics.…”

Spirophenylacridine‐2,7‐(diphenylphosphineoxide)‐fluorene: A Bipolar Host for High‐Efficiency Single‐Layer Blue Phosphorescent Organic Light‐Emitting Diodes

“…For the last 20 years, reaching stable and highly efficient blue PhOLEDs has been an intense research field worldwide . To date, all the high‐efficiency blue PhOLEDs (with external quantum efficiency (EQE) > 20%) are multilayer devices, which are constituted of a stack of organic layers in order to improve the injection, transport and recombination of charges within the EML. There are usually in a PhOLED stack, a hole‐transporting layer (HTL), an electron‐transporting layer (ETL), a hole‐blocking layer (HBL), and an electron‐blocking layer (EBL) and these layers can even be doubled.…”