N-coumarin derivatives as hole-transporting emitters for high efficiency solution-processed pure green electroluminescent devices

• N-coumarin derivatives as solution-processed hole-transporting green emitters.
• Fine-tuning of emission color by oligothiophenes and carbazole dendron substitutions.
• Morphologically stable amorphous thin films with high glass-transition temperatures.
• High efficiency solution-processed pure green OLEDs (λEL = 517 nm; CIE = 0.27, 0.62 and η = 9.45 cd A−1).

A series of new N-coumarin dyes containing oligothiophenyl N-coumarins as cores and carbazole dendrons up to the third generation as substituents were synthesized and characterized. Their optical, thermal, electrochemical, and electroluminescent properties as non-doped solution-processed hole-transporting light-emitters for electroluminescent devices were investigated. It was found that by incorporating carbazole dendrons in the molecule, we were able to reduce the crystallization and maintain the high emissive ability of a planar N-coumarin fluorescent core in the solid state as well as improve the thermal stability of the material. These N-coumarins showed a bright green fluorescence and could form morphologically stable amorphous thin films with glass-transition temperatures as high as 299 °C. Simple structured solution-processed organic light-emitting diodes using these dyes as emissive layers emitted a stable green electroluminescence (λEL = 517 nm) with high luminance efficiencies (up to 9.45 cd A−1 at 6.7 mA cm−2) and high green color purity.

New N-coumarin dyes containing oligothiophenyl N-coumarins as cores and carbazole dendrons as substituents show great potential as non-doped solution-processed hole-transporting light-emitters for electroluminescent devices. The devices using these dyes as emissive layers emit a stable green electroluminescence (λEL = 517 nm) with high luminance efficiencies (up to 9.45 cd A-1 at 6.7 mA cm-2) and high green color purity. Figure optionsDownload as PowerPoint slide