Organic light-Emitting diode based on bis(10-phenylanthracen-9-yl)benzene derivatives with a stable white emission

Highlights

• We synthesized a white material based on bis(10-phenylanthracen-9-yl)benzene.

• The effective exciplex and electroplex formation lead to the stable white emission.

• This material has good potential for applications in white OLEDs.

Abstract

In this work, we used the Suzuki cross-coupling reaction to synthesize the following two emitting materials: 1,3-bis(10-phenylanthracen-9-yl)benzene (1) and 2,6-bis(10-phenylanthracen-9-yl)pyridine (2). To investigate the electroluminescent (EL) properties of these materials, multilayered organic light-emitting diodes (OLEDs) devices were fabricated in the following sequence: indium-tin-oxide (ITO) (180 nm)/4,4′-bis(N-(1-naphthyl)-N-phenylamino)biphenyl (NPB) (50 nm)/emitting materials (1 and 2) (40 nm)/tris(8-hydroxyquinolinato)aluminium (Alq₃) (15 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). Of special significance, a device using 1 as an emitting material showed a white emission with maximum luminance, luminous, power, and external quantum efficiency values of 1727 cd/m², 1.74 cd/A, 0.78 lm/W, and 0.67% at 20 mA/cm², respectively, as well as CIE coordinates of (0.31, 0.44) at 7 V. Another device using 2 exhibited a sky-blue emission with maximum luminance, luminous, power, and external quantum efficiency values of 2279 cd/m², 1.95 cd/A, 0.97 lm/W, and 0.93% at 20 mA/cm², respectively as well as CIE coordinates of (0.24, 0.29) at 7 V.

Introduction

Organic light-emitting diodes (OLEDs) have been developed since the pioneering research of Tang and VanSlyke [1] due to the considerable potential regarding to the realization of full-color display and solid-state lighting [2], [3], [4]. The search for efficient white OLEDs has been regarded as one of the especially important issue because they are fundamental components in the realization of both full-color displays and solid-state lighting [5]. A number of examples of the realization of white emission OLEDs exist, whereby two (sky blue and orange emitters) or three (red, green, and blue) emitters are used with proper combination of fluorescent or phosphorescent materials in emitting layer [6]. Recently, many groups report the white OLEDs using a single emitter which could emit a white color using a combination of monomer sky blue and orange emissions from bimolecular recombination states such as excimer, exciplex, electroplex, and electromer [7], [8], [9].

Numerous building blocks such as anthracene [10], [11], [12], fluorene [13], carbazole [14], and pyrene [15] are research subjects in the preparation of different kinds of OLED materials; in particular, anthracene and its derivatives have been extensively studied for their excellent characteristics such as unusual photoluminescent properties, a sound electroluminescent performance, and an easier modification capability. The modifications at the 9- and 10-positions of the anthracene are especially easy, and numerous studies on this concept exist [16].

As part of the continuing efforts in the development of the efficient white OLED emitters, we synthesized two fluorescent materials, 1,3-bis(10-phenylanthracen-9-yl)benzene (1) and 2,6-bis(10-phenylanthracen-9-yl)pyridine (2). Both of these materials consist of two phenylanthracene that are connected through different central moieties such as benzene and pyridine at the 9-position of anthracene. The white emission could be obtained from the device using 1 or 2 as the single emitting material, if the monomeric blue emission of either 1 or 2 could be combined with the orange emission from the bimolecular recombination states (excimer, exciplex, electroplex, and electromer) of 1 or 2. In this paper, we present a device using 1 as an emitting material shows a stable white emission.