White organic light-emitting diodes (OLEDs) have been attracted much attention due to the potential applications in illumination light source and back light for liquid crystal display (LCD) as well as full color displays. A general solution to realizing white color OLEDs is to use separate multiple emitter-layers to produce different colors. The white light is achieved based to the color mixing. Unfortunately

the electroluminescent (EL) performances of this kind of devices such as color stability and efficiency still need improved. An optical microcavity has a structure with at least one space dimension on the order of optical wavelength. In a microcavity device

only one or a few optical modes are able to interact with the materials inside. Thus

the interaction between material and light within microcavity is greatly changed comparing with the condition of free space. To obtain white light in MOLED

a multimode within the emission spectrum of the wide-band emitter is essential

and can be realized by charging cavity length. However

for the white MOLED with multiple layer structure

the EL performances were seldom reported. We report the realization of a bright white MOLED with a simple two-layer structure and only one emitter layer.An microcavity organic light-emitting diode (MOLED) was developed to emit white light. The MOLED was designed and fabricated with a simple structure of glass/DBR/ITO(194 nm)/NPB(93 nm)/Alq

3

(49 nm)/MgAg(150 nm). White light was observed based to the emission of two cavity modes despite only one emitter layer. By well adjusting the resonance wavelength (488 and 612 nm) and intensity

the two cavity modes give rise to a bright

white electroluminescene emission with a maximum luminance of 16 435 cd/m

2

maximum luminous efficiency of 11.1 cd/A. At the typical luminance of 100 cd/m

2

the luminous efficiency

voltage and current density are 9 cd/A

6 V and 1.2 mA/cm

2

for the MOLED device

respectively. The MOLED has a CIE chromaticity coordinate of (0.32

0.34)

which is very stable under different applied voltage. The result indicated that microcavity is an efficient structure to construct white OLED.