Investigation on Organic Electroluminescent Diode as New Optical Source

有机电致发光（EL）二极管作为显示器件被逐步开发。在此应用中，我们利用发射到平面EL二极管的法线方向的光。由于光在有机层中各向同性地产生，因此一些光可以传播到切向方向并且从器件的侧端发射。在本研究中，从EL二极管的侧端发射的光的光谱，角分布和偏振进行了实验观察和研究，并与那些在正常方向进行比较。（1）光谱特征从侧端发射光谱中峰值强度处的波长短于法线方向。从侧端发出的光的光谱宽度比法线方向的窄。在发射区尺寸为6mm的器件中观察到了明显的光谱特性。（2）角分布观察到从发射面积尺寸为6mm的EL二极管的侧端发出的光强烈地发射到远离切线方向40度的方向。在发射面积较窄的器件中，强发射的方向角大于40 °。随着发射波长的增加，该角度向较小的角度移动。我们认为这些特性与EL二极管中的光传播有关。（3）偏振特性向法线方向发射的光不偏振，但是来自侧端的光在EL二极管的法线方向上轻微偏振。这种偏振特性与不同颜色EL二极管中的偏振特性相似。

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.