Enhancement of the Color Stabilization in Yellow Organic Light-Emitting with N, N′-bis-(1-naphthyl)-N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine/5,6,11,12-tetraphenylnaphthacene Multiple Heterostructures Acting as an Emitting Layer

The optical properties of organic light-emitting devices (OLEDs) with multiple heterostructures consisting of N, N′-bis-(1-naphthyl)-N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine(NPB)/5,6,11,12-tetraphenylnaphthacene (rubrene) emitting layers were investigated. The optical properties of the OLEDs were significantly affected by the number of heterostructures. The electroluminescence intensity corresponding to the rubrene peak for the OLEDs increased with increasing driving voltage and with increasing number of heterostructures. The Commission Internationale de l'Eclairage (CIE) chromaticity coordinates became stabilized with increasing the number of heterostructures, and the coordinates maintained almost constant, regardless of the driving voltage. The CIE chromaticity coordinate of the OLEDs with 5-periods of the heterostructures was (0.37, 0.54), indicative of a yellow color.