Starburst DCM‐Type Red‐Light‐Emitting Materials for Electroluminescence Applications

Abstract

Three new starburst DCM (4‐(dicyanomethylene)‐2‐methyl‐6‐[4‐(dimethylaminostyryl)‐4H‐pyran]) derivatives, 4,4′,4′′‐tris[2‐(4‐dicyanomethylene‐6‐t‐butyl‐4H‐pyran‐2‐yl)‐ethylene]triphenylamine (TDCM), 4,4′,′′‐tris[2‐(4‐(1′,3′‐indandione)‐6‐t‐butyl‐4H‐pyran‐2‐yl)‐ethylene]triphenylamine (TIN), and 4‐methoxy‐4′,4′′‐bis[2‐(4‐(1′,3′‐indandione)‐6‐t‐butyl‐4H‐pyran‐2‐yl)‐ethylene]triphenylamine (MBIN), have been designed and synthesized for application as red‐light emitters in organic light‐emitting diodes (OLEDs). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) reveal their extremely high glass‐transition temperatures and decomposition temperatures, as well as their low tendency to crystallize. Photoluminescence and electroluminescence measurements show that they exhibit a greatly restricted concentration‐quenching effect compared to DCM1 (4‐(dicyanomethylene)‐2‐methyl‐6‐[p‐(N,N‐dimethylamino)‐styryl]‐4H‐pyran), a simple but typical DCM‐type dye, as a result of their non‐planar, three‐dimensional structures that result from their unique propeller‐like triphenylamine electron‐donating cores. The peripheral electron‐withdrawing moieties also play a key role in the restriction of concentration quenching. That is, TIN and MBIN, bearing 1,3‐indandione acceptors, emit more efficiently than TDCM and DCM1, which have dicyanomethylene as acceptors at a high doping concentration of 10 wt.‐% in poly(9‐vinylcarbazole) (PVK) film, irrespective of whether they are photoexcited or electroexcited, though their fluorescence quantum yields in dilute solutions are much lower than that of DCM1. By way of the co‐doping approach, the electroluminescence device with the configuration indium tin oxide (ITO)/PVK:MBIN(10 wt.‐%):tris(4‐(2‐phenylethynyl)‐phenyl)amine (TPA; 30 wt.‐%) (70 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 20 nm)/tris(8‐quinolinolato) aluminum (Alq3;15 nm)/LiF (0.3 nm)/Al (150 nm) exhibits a turn‐on voltage of 5.1 V, a maximum luminance of 6971 cd m–2, a maximum efficiency of 6.14 cd A–1 (405 cd m–2), and chromaticity coordinates of (0.66,0.33). The encouraging electroluminescence performance suggests potential applications of the starburst DCM red‐light emitters in OLEDs.

Synthesis and pH‐sensing Properties of a Push–Pull Conjugated Fluorophore Based on Dicyanomethylene‐1,4‐dihydropyridine

“…The synthetic route to DCMP is shown in Scheme . Intermediate (2‐methyl‐6‐phenyl‐4 H ‐pyranylidene)malononitrile ( 4 ) was synthesized in good yield by minor modification of a reported method . Pyran 4 was reacted with an excess of 2‐(2‐aminoethoxy)ethanol in DMF to afford dihydropyridin‐4(1 H )‐ylidene)malononitrile ( 5 ), which was then readily transformed to pyridin‐4(1 H )‐ylidene)malononitrile (DCMP) in good yield by Knoevenagel condensation with 4‐(diethylamino)benzaldehyde in the presence of piperidine and molecular sieves in DMF.…”

Linear and V-Shaped Nonlinear Optical Chromophores with Multiple 4H-Pyran-4-ylidene Moieties

“…Concerning the 1D-derivatives 9 and 11 , theoretical calculations show that both geometries are nearly isoenergetic (within 1 kcal/mol), and in fact, both of them have been considered in the literature for closely related dyes. , To study their structure in solution, we have carried out NOE experiments on compound 9a in CDCl 3 at room temperature. They show a NOE between H a (but not H b ) and the nearby H atom of the pyranylidene ring, thus demonstrating that 9a exists in solution in s - trans geometry (Figure ), the same displayed by the analogous compound DCM and related derivatives in the solid state …”

Amorphous Fluorescent Organic Emitters for Efficient Solution-Processed Pure Red Electroluminescence: Synthesis, Purification, Morphology, Solid-State Photoluminescence, and Device Characterizations

“…1 and 2 featured a broad emission with an unusual well-formed lower energy shoulder in solution, which cannot be attributed to the potential residual impurities in the samples based on the spectral shape and no “detectable” evidence of impurities by our current analytical methods. The same phenomenon occurred in some DCM-type red-light-emitting dyes and requires further understanding …”