Investigation on Organic Electroluminescent Diode as New Optical Source

有机电致发光二极管作为一种显示器件逐步得到发展。在这个应用中，我们利用光发射到平面EL二极管的法线方向。由于光在有机层中是各向同性产生的，因此一些光可以向切向传播并从器件的侧端发射。在本研究中，实验观察了从EL二极管侧端发射的光的光谱、角分布和偏振，并与法线方向的光进行了比较。(1)光谱特征侧端发射光谱中峰值强度处波长短于在法向。侧端光的光谱宽度比法向光窄。这些光谱特征在发射区尺寸为6mm的器件上得到了明显的观察。(2)角度分布从发光面积为6mm的EL二极管侧端发出的光向远离切向40度方向强烈发射。在发射区域较窄的器件中，强发射的方向角大于40度。随着发射波长的增加，该角度向较小的角度偏移。我们认为这些特性与光在EL二极管中的传播有关。(3)偏振特性向法线方向发射的光不发生偏振，但从侧端发出的光在EL二极管法线方向发生轻微偏振。这种偏振特性与不同颜色的发光二极管相似。

The organic electroluminescent(EL) diode was progressively developed as a display device. In this application, we utilize the lights emitted to the normal direction of the planar EL diode. As the lights are isotropically generated in the organic layer, some of the lights can propagate to the tangential direction and emit from the side end of the device. In this research, the spectrum, angular distribution and polarization of the lights emitted from the side end of the EL diode were experimentally observed and investigated in comparison with those in the normal direction.(1)Spectral featuresThe wavelength at the peak intensity in the emission spectrum from the side end was shorter than that in the normal direction. The spectral width of the lights from the side end was narrower compared with that in the normal direction. These spectral characteristics were obviously observed in the device of the emission area size of 6mm.(2)Angular distributionThe lights from the side end of the EL diode with the emission area size of 6mm were observed to be strongly emitted to the direction of 40 degree away from the tangential direction. In the device with narrower emission area, the direction angle of the strong emission was larger than 40 degree. With longer emission wavelengths, this angle was shifted to the smaller one. We expect that these charactristics are related to the light propagation in the EL diode.(3)Polarization characteristicsThe lights emitted to the normal direction were not polarized, but the lights from the side end were slightly polarized in the normal direction of the EL diode. This polarization characteristics was similar to that in different color EL diode.