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

Abstract

Advances in achieving high external quantum efficiency (EQE) of near‐infrared (NIR) organic light‐emitting diodes (OLEDs) are lagging behind that of the visible‐light OLEDs, according to the energy gap law. Herein, two structurally simple NIR‐phosphorescent Ir(III) complexes, DTCNIr and PTCNIr, with the cyclometalated ligands functionalized by the 1‐phenylisoquinoline‐4‐carbonitrile moiety and thieno/benzo[b]thiophene moiety are handily accessed within three synthetic steps. The introduction of the cyano unit can significantly lower the lowest unoccupied molecular orbitals whereas incorporating the conjugated group can elevate the highest occupied molecular orbitals of the newly designed Ir(III) complexes. The intramolecular charge transfer (ICT) transitions are enhanced due to the increased donor–acceptor interaction inside the metallophosphor. As a result, the emissions are red‐shifted to the NIR region with fast radiative decay. A maximum external quantum efficiency (EQE) of 8.11% with the emission peak at 726 nm for DTCNIr and a maximum EQE of 6.39% with the emission peak at 763 nm for PTCNIr are achieved in the NIR OLEDs by using these Ir(III) materials as the dopant emitters, a champion efficiency in the Ir(III)‐based OLEDs with the emission peak exceeding 760 nm.

Design, Synthesis and Photophysical Studies of Luminescent Rhodium(III) Complexes in Near‐Infrared Region

“…Among various NIR luminescent materials, transition-metal (TM) complexes have been considered as a promising candidate due to their efficient triplet exciton harvesting effect, easier structure modification, energy tunability, unique spectroscopic features and moderate luminescent efficiency. [7] In the past two decades, a number of ruthenium(II), [8] osmium(II), [9] platinum(II) [10] and iridium(III) [11][12][13][14][15][16][17] complexes have been reported to demonstrate NIR luminescence. Iridium(III) complexes with 1-(benzo [b]thiophen-2-yl)-isoquinolinate ligand were found to show luminescence in the region of 680-850 nm and have been successfully applied as NIR triplet emitter in OLEDs.…”

Engineering of Cyano Functionalized Benzo[d]imidazol-2-ylidene Ir(III) Phosphors for Blue Organic Light-Emitting Diodes

“…Herein, we reported a new series of Ir­(III) phosphors bearing three distinctive benzo­[ d ]­imidazol-2-ylidene cyclometalates, which mainly differed in the position of cyano and CF 3 substituents. The cyano substituent was chosen for this study as it has been widely employed in modifying the fundamental characters of various optoelectronic materials. − Their molecular structures are depicted in Scheme , namely, m - / f -Ir­(mfcp) 3 , m - / f -Ir­(ofcp) 3 , and m - / f -Ir­(5-mfcp) 3 with mfcp, ofcp, and 5-mfcp chelates, which stand for 4-cyano-3-methyl-1-phenyl-6-(trifluoromethyl)-benzo­[ d ]­imidazol-2-ylidene, 5-cyano-1-methyl-3-phenyl-6-(trifluoromethyl)-benzo­[ d ]­imidazol-2-ylidene, and 1-(3-( tert -butyl)­phenyl)-6-cyano-3-methyl-4-(trifluoromethyl)-benzo­[ d ]­imidazol-2-ylidene, respectively. Notably, the cyano substituent is employed for its effective electron-withdrawing capability, while its varied spatial distance from the parent benzo­[ d ]­imidazol-2-ylidene fragment will be the next important parameter. − Our studies revealed the highest photoluminescence quantum yields of 94.5% and fastest radiative lifetime of ∼1.0 μs in degassed toluene solution at RT, as observed for m -Ir­(mfcp) 3 .…”

High-efficiency deep-red to near-infrared emission from Pt(ii) complexes by incorporating an oxygen-bridged triphenylborane skeleton

“…Organic luminescent materials in the deep-red to near-infrared region have become a hotspot in displays and solid lighting due to their broad applications in night vision displays, information security equipment, photodynamic therapy and organic light-emitting diodes (OLEDs). 1–10 In the past few decades, a series of highly efficient phosphorescent complexes of iridium (Ir), 11–14 osmium (Os) 15–18 and platinum (Pt) 19–26 have been developed by virtue of the heavy atom effect with an intrinsic 100% internal quantum efficiency. However, due to the limitations of the energy gap law and quenching effect in the aggregation state, there are still great difficulties in innovatively developing long-wavelength and high-efficiency near-infrared (NIR) luminescent materials.…”