Red‐Emitting Fluorenes as Efficient Emitting Hosts for Non‐Doped, Organic Red‐Light‐Emitting Diodes

Abstract

Rare red‐fluorescent fluorene derivatives have been designed and synthesized. The long‐wavelength red fluorescence is achieved by incorporating a di(4‐tolyl)amino or diphenylamino electron donor and a dicyanovinyl electron acceptor. The single‐crystal X‐ray structures of the di(4‐tolyl)amino (pTSPDCV) and diphenylamino (PhSPDCV) compounds indicate only weak non‐π van der Waals contacts in addition to long‐distance dipole–dipole interactions of the red‐emitting fluorene molecules in the solid state. The aggregation of the dipolar fluorene is largely suppressed by introducing bulky 9,9‐substituents (spiro‐fused bifluorene) as well as a non‐planar di(4‐tolyl)amino or diphenylamino group. In the solid state, these fluorene derivatives all show red fluorescence that is much brighter than with the red dopants Nile Red and DCM (4‐(dicyanomethylene)‐2‐methyl‐6‐[4‐(dimethylaminostyryl)‐4H‐pyran]). The unique photophysical properties of red‐emitting fluorene derivatives differ from other known red dopants and facilitate the fabrication of non‐doped red organic light‐emitting diodes (OLEDs). Authentic red (CIE, x = 0.65, y = 0.35) electroluminescence with a brightness of more than 12 000 cd m–2 (greater than 600 cd m–2 at 20 mA cm–2) and a remarkable external quantum efficiency as high as 3.6 % have been observed for the red‐emitting OLEDs with pTSPDCV or PhSPDCV as the sole emitting host.

Conjugated Organosilicon Materials for Organic Electronics and Photonics

“…This compound has an increased chromophore stacking distance in the crystal (5.5 Å vs 3.4 Å for TIPS-5AC-DO) and allowed a concentration up to 2% of dopant in both Alq 3 and NPD matrixes without formation of aggregates. OLEDs prepared from such composites showed bright red emission with an external electroluminescence quantum yield of 3.3% [47], close to the theoretical maximum and also very close to the highest value reported (3.6%) [48] for a small-molecule red-emissive OLED.…”

RGD-conjugated two-photon absorbing near-IR emitting fluorescent probes for tumor vasculature imaging

“…Pd-catalyzed Buchwald-Hartwig amination coupling was employed for the arylamination of L in the presence of Cs 2 CO 3 to yield 7-(diphenylamino)-9,9-dihexyl-9H-fluorene-2-carbaldehyde ( M ). 19 The two key steps that followed involved the Knoevenagel condensation between M and 2-(2,6-dimethyl-4H-pyran-4-ylidene)malononitrile to produce (E)-2-(2-(2-(7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl)vinyl)-6-methyl-4H-pyran-4-ylidene)malononitrile ( N ) and subsequent reaction between N and Q leading to 6-(4-((E)-2-(4-(dicyanomethylene)-6-((E)-2-(7-(diphenylamino)-9,9-dihexyl-9H-fluoren-2-yl)vinyl)-4H-pyran-2-yl)vinyl)-2,6-dimethoxyphenoxy)hexanoic acid ( 3) (Scheme 3). Organic nanoparticles of dicyanopyranyl 3 by slowly adding a THF solution of 3 into distilled water (forming organic nanoparticles designated as 3a ) or lecithin aqueous solution to form surfactant stabilized organic nanoparticles (designated as 3b ).…”

Organic Light‐Emitting Diodes with Field‐Effect‐Assisted Electron Transport Based on α‐bi;,ω‐bi;‐Diperfluorohexyl‐quaterthiophene

“…In conventional OLEDs high quantum efficiencies have been reported, [14][15][16][17][18][19] even approaching an internal quantum efficiency of 100%. [20] However, in these devices the point of maximum external quantum efficiency is typically reached at low current densities (in the order of 10 À2 A cm À2 ) because of increased nonradiative losses at higher voltage biases.…”