Tuning the Photophysical and Electroluminescence Properties in Asymmetrically Tetrasubstituted Bipolar Carbazoles by Functional Group Disposition

• DOI: 10.1021/acsami.8b04566
• Publication Date: 2018-06-22T10:34:40Z
• Authors: Rajendra Kumar Ko...; K. R. Justin Thomas; Ambika Pathak; Deepak Kumar Dubey; Snehasis Sahoo; Jwo-Huei Jou
• Keywords: Triphenylamine; Carbazole; Solvatochromism; Acceptor; Chromophore; HOMO/LUMO

Carbazoles decorated with both donor and acceptor fragments offer a classical way to optimize bipolar functional properties. In this work, series of carbazoles featuring triphenylamine donors cyano acceptors are synthesized their structure-property relationship is studied. The effects connectivity the chromophore number density on photophysical electroluminescence properties investigated. position 3,6-dicyanocarbazole nucleus significantly affected dye possessing C2 C7 displayed red shift in absorption when compared structural analogue tethered C1 C8. emission wavelength dyes tunable from blue green, by altering substituents. All exhibited positive solvatochromism emission, attributable photoinduced intramolecular charge transfer acceptor. However, extent hybridization local charge-transfer-excited states highly dependent groups carbazole nucleus. Dyes containing substituents at showed prolonged excited state lifetime, broad large Stokes shifts, indicating presence higher component state. exceptional thermal stability onset decomposition temperature (10% weight loss) > 350 °C. Electrochemical measurements revealed low oxidation potential for C3 and/or C6. Addition led stabilization lowest unoccupied molecular orbital. Furthermore, materials were tested as emitting dopants solution-processable multilayer organic light diodes found display deep-blue/sky-blue external quantum efficiency high 6.5% deep-blue emitter (CIE y ∼ 0.06).