Electrical and optical characteristics of red organic light-emitting diodes doped with two guest dyes

Abstract

We report the red organic light-emitting diodes doped with rubrene and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). N,N′-Diphenyl-N,N′-bis(1-naphthyl)-(1,1′-biphenyl)-4,4′- diamine (NPB) and doped tri-(8-hydroxyquinoline)aluminum (Alq3) are used as hole and electron-transport layers, respectively. The performances of the co-doped diodes are found to be improved compared to only DCJTB doped diodes. We attribute the improvement to rubrene that assists the energy transfer from Alq3 to DCJTB more efficiency. The energy transfer rates from Alq3 to DCJTB, from Alq3 to rubrene, and from rubrene to DCJTB are proximately calculated to be 1.04×109, 3.89×109, and 2.79×109s-1 according to the fit of the fluorescence decay curves, respectively. It can be seen clearly that the energy transfer rate from Alq3 to DCJTB through rubrene is 2.7 times higher than that from Alq3 to DCJTB directly. © 2003 Elsevier Science B.V. All rights reserved.