Issue 35, 2008

Solution-processable organic fluorescent dyes for multicolor emission in organic light emitting diodes

Abstract

Four novel fluorescent dyes, bis(difluorenyl)amino-substituted carbazole 1, pyrene 2, perylene 3, and benzothiadiazole 4, were synthesized by C–N cross-coupling with a palladium catalyst. These dyes are soluble in common organic solvents, and their uniform films were formed by spin-coating from their solutions. Their glass transition temperatures were sufficiently high (120–181 °C) to form amorphous films for organic light emitting diodes. These solution processable dyes exhibited strong photoluminescence (PL) in the film form (1: sky blue, 2: blue-green, 3: yellow, and 4: deep red). Optical and electrochemical properties of the compounds were investigated with photoelectron spectroscopy and cyclic voltammetry. The energy levels obtained from both measurements were in good agreement, and those levels were related to the electronic properties of the central core; the electron-donating carbazole compound showed the lowest ionization potential and the electron-withdrawing benzothiadiazole compound showed the largest electron affinity. Simple double layer devices were prepared with these fluorescent dyes as emitting layer and bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium(III) (BAlq) as a common hole blocking layer for each color. Electroluminescence colors were the same as those of the PL spectra in each compound. These multicolor electroluminescences show that these conjugated oligomers can be candidates for solution processable light emitting materials for OLEDs as well as conjugated polymers or dendrimers.

Graphical abstract: Solution-processable organic fluorescent dyes for multicolor emission in organic light emitting diodes

Supplementary files

Article information

Article type
Paper
Submitted
11 Apr 2008
Accepted
11 Jun 2008
First published
24 Jul 2008

J. Mater. Chem., 2008,18, 4183-4188

Solution-processable organic fluorescent dyes for multicolor emission in organic light emitting diodes

Y. Pu, M. Higashidate, K. Nakayama and J. Kido, J. Mater. Chem., 2008, 18, 4183 DOI: 10.1039/B806160B

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