Electroluminescence of 6-R-1,3-diphenyl-1H-pyrazolo[3,4-b]quinoline-based organic light-emitting diodes (R = F, Br, Cl, CH3, C2H3 and N(C6H5)2)

A series of 6-substituted-1,3-diphenyl-1H-pyrazolo[3,4-b]quinoline, 6-R-DPPQ[R=F, Br, Cl, CH3, C2H3, N(C6H5)(2)] has been synthesized and characterized by spectroscopic methods. The photoluminescence (PL) is measured in the organic solutions of different polarities and found to be highly solvatochromic. The large difference between the excited- and state-dipole moments indicates on strong intramolecular charge transfer. The EL spectra are obtained for the fabricated OLEDs with a general structure of EL device ITO/PVK:6-R-DPPQ/Ca/Al. The blue emission originating from PVK matrix appears to be quenched in the EL spectra of doped PV-K.:6-R-DPPQ layer giving rise to emission in blue-green or green spectral regions. The obtained results demonstrate that a series of newly synthesized DPPQ-derivatives may be considered as prospective materials for electroluminescent applications. (c) 2006 Elsevier B.V. All rights reserved.