White OLEDs (WOLEDs) have attracted much attention for several applications, such as backlights in LCD, full-color
OLED display using on-chip color filters, and low cost illumination sources. OLEDs have typically very broad emissions,
which makes them uniquely suitable for light source applications. In this paper, some fundamentals of the CIE
colorimetry system including the color-rendering index are described. Given the spectral power distribution of WOLED,
the parameters of a light source (chromaticity coordinate, CCT, CRI, and the luminous efficacy) can be calculated. A
MATLAB program for this purpose is developed in this paper.
WOLEDs utilizing two primary-color emitters are fabricated. NPB doped with 2% Rubrene is used as the red-emitting
layer and anthracene derivative as the blue-emitting layer. With a structure of ITO/2TNATA(20nm)/NPB(20 nm)/
NPB:rubrene(2%)(10nm)/ anthracene (30 nm)/Alq3(20nm)LiF(1nm)/Al(100nm), a white light with CIE coordinates of
(0.34, 0.37) is generated. The color properties are presented in this paper. The results show that the white color can be
created from numerous combinations of different spectra. Based upon this, the characterization of the WOLED is
simulated and the design of WOLED for illumination is discussed.
In contrary to light source applications where illumination quality white is the most important, all colors are equally
important for display applications. The white spectrum of the two-emitter WOLED is transmitted through the typical red,
blue and green color filters. The performance of this color display is simulated and the WOLED design for display
application is discussed.