White top-emitting organic light-emitting diodes employing a heterostructure of down-conversion layers

We investigate white top-emitting organic light-emitting diodes (OLEDs) based on a heterostructure of down-conversion (DC) layers. The white DCOLED comprises consecutive organic conversion layers of 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) doped in a matrix of tris(8-hydroxy-quinolinato)aluminum (Alq3), and N4,N41′-bis-(4-tert-butyl-phenyl)-N4,N4′-di-fluoranthen-3-yl-diphenylether-4,4′-diamine (OYSE). The DC layers also function as capping layers to enhance the light outcoupling and optical modification of the underlying blue OLED. White light emission with CIE color coordinates of (0.27, 0.26) and a color rendering index of 60 is achieved. Furthermore, the spectral angular dependence of the white device is examined.

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► Top emitting white OLEDs based on heterostructure of down conversion layers.
► Light outcoupling enhancement by capping layers.
► Microcavity effects in down conversion OLEDs.