Highly Efficient and Stable Red Organic Light-Emitting Devices Using 9,10-Di(2-naphthyl)anthracene as the Host Material

Abstract

We present red organic light-emitting devices (OLEDs) with high efficiency and stability based on a wide band gap host material 9,10-di(2-naphthyl)anthracene (ADN). In these devices, N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) and tris(8-hydroxy-quinoline) aluminum (Alq) were used as hole and electron transport layers, respectively. Coumarin 6 (C6) and 4-(dicyano-methylene)-2-t-butyl-6-(1,1,7,7-tetramethyl-julolidyl-9-enyl)-4H-pyran (DCJTB) were co-doped into the ADN emitting layer. Utilizing the two-step energy transfer from ADN to C6 and then from C6 to DCJTB, we achieved pure red organic light-emitting devices, which showed improved optical and electrical characteristics. Compared with devices where the emitting layer is composed of Alq and DCJTB, the emission efficiency and stability of the co-doped ADN-based devices are greatly improved and the turn-on voltage is also decreased. The co-doping technique provides a promising way to utilize wide band gap materials as the host to make red OLEDs, which will be useful in improving the EL performance of devices and simplifying the process of fabricating full-color OLEDs.