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

Abstract 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-4 H -pyran (DCM) doped in a matrix of tris(8-hydroxy-quinolinato)aluminum (Alq 3 ), and N 4, N 41′-bis-(4-tert-butyl-phenyl)- N 4, N 4′-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.