High-Color-Purity Organic Light-Emitting Diodes Incorporating a Cyanocoumarin-Derived Red Dopant Material

Abstract

This paper describes a red dopant material, the cyanocoumarin derivative 9-cyano-10-͑2-benzothiazolyl͒-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo ͓l͔ pyrano͓6,7,8-i j͔quinolizin-11-one ͑RC545T͒, and its use in organic light-emitting diodes ͑OLEDs͒. Because RC545T exhibits ͑i͒ redshifted fluorescence ͑ max = 607 nm͒ and ͑ii͒ a narrower full width at half-maximum ͑fwhm; 48 nm͒ relative to the corresponding signal for 4-͑dicyanomethylene͒-2-tert-butyl-6-͑1,1,7,7-tetramethyljulolidyl-9-enyl͒-4H-pyran ͑DCJTB; max = 605 nm; fwhm = 73 nm͒, which is currently one of the most efficient red dopant materials, we could fabricate red OLEDs exhibiting improved color purity. A device incorporating RC545T as a dopant and rubrene as an assistant dopant in the configuration indium-tin oxide ͑ITO͒/N,NЈ-bis͑1-naphthyl͒-N,NЈ-diphenyl-1,1Ј-biphenyl-4,4Ј-diamine ͑65 nm͒/tris͑8-hydroxyquinoline͒aluminum ͑Alq 3 ͒:15 wt % rubrene:2 wt % RC545T ͑30 nm͒/Alq 3 ͑30 nm͒/LiF ͑0.8 nm͒/Al ͑250 nm͒ exhibited a maximum luminance of 8000 cd/m 2 at 12.5 V, with near-saturated CIE coordinates of ͑0.64, 0.35͒, significantly better red color purity than that of the device featuring DCJTB as the dopant material ͓CIE coordinates: ͑0.63, 0.37͔͒, thereby rendering RC545T a good red-emitting dopant for OLED applications.

Simultaneous Singlet–Singlet and Triplet–Singlet Förster Resonance Energy Transfer from a Single Donor Material

“…33 The latter has to be normalized to unity and the former to the molar extinction coefficient, which is ϵ max = 4.02 × 10 4 /(mol cm) for DCJTB. 34…”

Design and Synthesis of Coumarin–Imidazole Hybrid Chromophores: Solvatochromism, Acidochromism and Nonlinear Optical Properties

“…There is a growing interest in the design and synthesis of imidazole derivatives with functional coumarin chromophores having extended π‐conjugation length to enhance their optical, charge transfer and nonlinear optical (NLO) properties . Coumarin containing compounds are extensively studied in different applicative areas such as hole transport material , bio‐imaging , sensing , OLEDs , optical brighteners and DSSCs . Coumarin derivatives can be functionalized with electron donating (D) and electron accepting (A) groups which reduce the HOMO‐LUMO energy band gap leading to redshifted absorption and emission .…”

Rapid Access of Alkynyl and Alkenyl Coumarins via a Dipyridinium Methylide and Propargylamine Cascade Reaction

“…4,5 A recent convergent synthetic tool, i.e., cross-coupling technology, 6 has emerged to allow rapid assembly of diversified coumarin structures. Particularly the alkynyl coumarins, which not only are found to be useful in pharmaceuticals 7 but also prevail in unique applications in functional organic materials, for instance laser dyes, 8,9 dye-sensitized solar cells (DSSCs), 10,11 organic lightemitting diodes (OLEDs), 12 semiconductors, 13 and photovoltaics, 14 are often synthesized by a Pd-catalyzed crosscoupling strategy.…”

“…Coumarin scaffolds are abundantly found in many natural products and biologically active intermediates, and constitute one of the most important structural motifs for developing new pharmaceuticals. − Coumarins containing an unsaturated lactone skeleton are classically synthesized by aldol or Knoevenagel condensations. , A recent convergent synthetic tool, i.e., cross-coupling technology, has emerged to allow rapid assembly of diversified coumarin structures. Particularly the alkynyl coumarins, which not only are found to be useful in pharmaceuticals but also prevail in unique applications in functional organic materials, for instance laser dyes, , dye-sensitized solar cells (DSSCs), , organic light-emitting diodes (OLEDs), semiconductors, and photovoltaics, are often synthesized by a Pd-catalyzed cross-coupling strategy.…”