Iridium(III) complexes with 1-phenylisoquinoline-4-carbonitrile units for efficient NIR organic light-emitting diodes

Abstract

Summary Achieving the high external quantum efficiency (EQE) of near-infrared (NIR) emission in iridium(III) complexes still remains a challenge owing to their unsteady excited states which easily decay to the ground states through the nonradiative pathways. Herein, three Ir(III) phosphors in which the cyclometalated ligand 1-phenylisoquinoline-4-carbonitrile (piq-CN) is functionalized with the cyano, tert- butyl, and dimethyl groups are developed (CN-CNIr, Bu-CNIr, and DM-CNIr, respectively). Three simple synthetic steps can afford this class of deep red to NIR Ir(III) emitters. The organic light-emitting diodes (OLEDs) based on Bu-CNIr and DM-CNIr attain the maximum EQEs of 7.1% and 7.2% with the emission peaks at 695 and 714 nm, respectively. This strategy using substituted piq-CN derivatives as the cyclometalated ligands can offer an effective approach to promote the radiative rate of NIR-emitting Ir(III) materials. An insight into how the electron-withdrawing and electron-donating substituents on ligands influence the optoelectronic properties of their Ir(III) complexes is also provided.

Boosting the efficiency of deep-red Ir(iii) complexes by modulating nitrogen atoms for high-performance OLEDs

“…[25][26][27] Despite some progress in molecular design, there are still relatively few Ir(III) complexes achieving deep-red emission as well as high photoluminescence and electroluminescence (EL) performance. [28][29][30][31] Therefore, a simple molecular design strategy is urgently needed for deep-red emitters.…”

High Performance NIR OLEDs with Emission Peak Beyond 760 nm and Maximum EQE of 6.39%

“…So far, the NIR OLEDs using the Ir(III) emitters with 1-phenylisoquinoline-4-carbonitrile derivatives offer a maximum EQE of 7.2% with the EL max at 714 nm. [33] There is still considerable room for improvement in both EQE value and emission wavelength compared to the NIR OLEDs based on Pt(II) and Os(II) emitters, let alone compared to the efficient NIR QDLEDs and PeLEDs.…”

714 nm emission with 12.25% efficiency from iridium complexes with low iridium content by the strategy of rigid coordination core and amplifying shell

“…In recent years, near-infrared (NIR) organic light-emitting diodes (NIR-OLEDs) with emission wavelengths from 700 to 2500 nm have shown potential applications in optical communication, bioimaging, chemosensors, night-vision, photodynamic therapy, etc. [1][2][3][4] Over the past two decades, in order to meet practical application, many NIR-emitting materials, including donor-acceptor (D-A) organic small molecules, 5,6 conjugated polymers, 7,8 transition metal complexes [9][10][11][12][13][14][15][16] and lanthanide-metal complexes, 17,18 have been developed. However, with increasing emission wavelengths, these NIR emitters usually displayed significantly descending luminescence efficiency because of the exponentially increased non-radiative deactivation pathways according to the ''energy-gap law''.…”