Achieving High Performances of Nondoped OLEDs Using Carbazole and Diphenylphosphoryl-Functionalized Ir(III) Complexes as Active Components

Abstract

Nondoped electroluminescent devices offer advantages over their doped counterparts such as good reproducibility, reduced phase separation between host and guest materials, and potential of lower-cost devices. However, low luminance efficiencies and significant roll-off values are longstanding issues for nondoped devices, and a rational design strategy for the preparation of efficient phosphors is highly desired. In this work, cyclometalated Ir(III) complexes 3CzIr(mtpy), 4CzIr(mtpy), 3POIr(mtpy), and 4POIr(mtpy) bearing carbazole (Cz) or diphenylphosphoryl (PhPO) groups substituted at different positions of 1,2-diphenyl-H-benzimidazole (HPBI) were designed and synthesized. Owing to the steric effects induced by these groups, a significant intermolecular interaction was avoided, thereby reducing self-quenching and triplet-triplet annihilation (TTA) at high brightness. Simultaneously, attached functional moieties manipulate the charge-carrier character and enhance the EL performance of the complexes. Device N3-10, based on 3POIr(mtpy), successfully realized excellent performance and improved efficiency stability, rendering a turn-on voltage of 2.5 V, a maximum current efficiency of 29.7 cd A, and a maximum power efficiency of 31.1 lm W, which are all almost 3-fold higher than that of the control device N-10 based on parent complex. Inspiringly, all of the devices showed reduced efficiency roll-off as luminance increased. To the best of our knowledge, these are good results for green-emitting PHOLEDs using vacuum evaporation techniques, and they provide fundamental insights into the future realization of efficient phosphorescent Ir(III) complexes and corresponding nondoped devices.

Influence of the Bite Angle of Dianionic C,N,C-Pincer Ligands on the Chemical and Photophysical Properties of Iridium(III) and Osmium(IV) Hydride Complexes

“…The HOMO energy levels determined from the oxidation potentials are in good agreement with those obtained from DFT calculations. Similarly, the LUMO energy levels determined from the onsets of the emission spectra, in MeTHF, at room temperature show the same trend as those obtained from DFT calculations.…”

Impact of Benzannulation Site at the Diimine (N^N) Ligand on the Excited-State Properties and Reverse Saturable Absorption of Biscyclometalated Iridium(III) Complexes

“…These characteristics spark research interest in exploring potential binding geometries with novel ancillary ligands. After the seminal work by Watts et al on triply ortho-metalated Ir­(III) complexes in the 1980s, diverse mono-, bis-, and triscyclometalated complexes with different polypyridine ligands or cyclometalating ligands have been reported. , Among these complexes, biscyclometalated monocationic Ir­(III) complexes are discovered to play a crucial role in various applications, such as sensitized photo-upconversion, organic light emitting diodes (OLEDs), − light-emitting electrochemical cells (LEECs), , photodynamic therapy, − nonlinear optics, − photocatalysis, − and bioimaging and biosensing …”

A phosphorescent OLED with an efficiency roll-off lower than 1% at 10 000 cd m−2 achieved by reducing the carrier mobility of the donors in an exciplex co-host system

“…The details of the synthetic conditions of BPhCz-pimi and BPhCz-mimi referred to the previous studies and can be found in the experimental section. [20][21][22] BCzPh-pimi and BCzPh-mimi can be readily dissolved in dichloromethane, chloroform, and toluene. Consequently, they were purified by column chromatography and identified by 1 H NMR spectroscopy, 13 C NMR spectroscopy, and high-resolution mass spectrometry.…”