A Highly Efficient, Blue‐Phosphorescent Device Based on a Wide‐Bandgap Host/FIrpic: Rational Design of the Carbazole and Phosphine Oxide Moieties on Tetraphenylsilane

Abstract

A new series of wide‐bandgap materials, 4‐dipenylphosphine oxide‐4′‐9H‐carbazol‐9‐yl‐tetraphenylsilane (CSPO), 4‐diphenylphosphine oxide‐4′,4″‐di(9H‐carbazol‐9‐yl)‐tetraphenylsilane (pDCSPO), 4‐diphenylphosphine oxide ‐4′‐[3‐(9H‐carbazol‐9‐yl)‐carbazole‐9‐yl]‐tetraphenylsilane (DCSPO), 4‐diphenylphosphine oxide‐4′,4″,4″′‐tri(9H‐carbazol‐9‐yl)‐tetraphenylsilane (pTCSPO) and 4‐diphenylphosphine oxide ‐4′‐[3,6‐di(9H‐carbazol‐9‐yl)‐9H‐carbazol‐9‐yl]‐tetraphenylsilane (TCSPO), containing different ratios and linking fashions of p‐type carbazole units and n‐type phosphine oxide units, are designed and obtained. DCSPO is the best host in FIrpic‐doped devices for this series of compounds. By utilizing DCzSi and DPOSi as hole‐ and electron‐transporting layers, a high EQE of 27.5% and a maximum current efficiency of 49.4 cd A−1 are achieved in the DCSPO/FIrpic doped device. Even at 10 000 cd m−2, the efficiencies still remain 41.2 cd A−1 and 23.0%, respectively.

Design, synthesis and characterization of a new blue phosphorescent Ir complex

“…1 (a), the absorption spectrum for Cz-C8-FIrpic shows a peak at 260 nm, which is related to the π−π* transition of 2-(2,4-difluorophenyl)pyridine ligands in the FIrpic unit. 30 The phosphorescent emission spectrum at low temperature was measured in frozen CH 2 Cl 2 . 26 Furthermore, the absorbance shoulder at 293 nm is attributed to the π−π* transition of the carbazole moiety.…”

Efficient Deep Blue Electroluminescence with an External Quantum Efficiency of 6.8% and CIEy < 0.08 Based on a Phenanthroimidazole–Sulfone Hybrid Donor–Acceptor Molecule

“…1,2 While blue phosphorescent materials based on transition metal complexes, such as iridium (Ir) complexes, have already realized external quantum efficiency (EQE) over 20%, 3 they suffer from sharp efficiency roll-off at high brightness. 4 Furthermore, performance of deep blue phosphors still remains unsatisfactory because the nonradiative process via metal d-orbitals becomes competitive when elevating the radiative metal-ligand charge-transfer (MLCT) excited state into the deep blue region.…”

Using an Organic Molecule with Low Triplet Energy as a Host in a Highly Efficient Blue Electrophosphorescent Device

“…Apart from possessing hole-and electron-transporting mobility, it is universally believed that bipolar host materials for blue PhOLEDs should have higher triplet energies than the blue phosphors. [6] Therefore, it is preferable to achieve a trade-off between the triplet energy and HOMO/LUMO level for host materials. [4] To guarantee high triplet energies, wide band-gap bipolar host materials have been developed, such as bis [4-(N-carbazolyl)phenyl]phenylphosphine oxide (BCPO), 2,7-bis [diphenylphosphoryl]-9-[4-(N,N-diphenylamino)phenyl]-9-phenylfluorene (POAPF), and 9-[3-(9H-carbazole-9-yl)phenyl]-3-(diphenylphosphoryl)-9H-carbazole (mCPPO1), which usually emit fluorescence in violet or ultraviolet region.…”

“…[5] However, owing to their intrinsic low HOMO level and high LUMO level, simultaneously injecting holes and electrons into these wide band-gap bipolar host materials would be difficult, which could consequently bring about high drive voltages and low power efficiencies in the blue PhOLEDs. [6] Therefore, it is preferable to achieve a trade-off between the triplet energy and HOMO/LUMO level for host materials.…”