温度和电压对双层有机发光二极管复合效率的影响

Effect of Temperature and Applied Voltage on the Recombination Efficiency in Double Layer Organic Light Emitting Diodes

提出了双层有机电致发光二极管ITO PPV PBD Ca复合的理论模型。计算并讨论了温度和电压对其复合效率的影响 :在电压为 6～ 7 5V时 ,复合效率随温度变化出现两个峰值 ,但随着电压升高 ,两峰值相互靠拢 ,当电压达到 9V时 ,峰值位置重叠 ,我们认为这一现象除了浅缺陷能级和深缺陷能级贡献的结果以外 ,还由于复合区域发生变化引起的。

In this paper, the theoretical model of recombination was presented and the effect of temperature and applied voltage on the recombination efficiency was investigated in double layer organic light-emitting diodes: ITO/PPV/PBD/Ca. At lower applied voltage, two peaks have been observed in the curve of recombination efficiency vs. temperature. With increasing voltage, the two peaks shifted toward each other, and at voltage around 9 V the two peaks converged. These phenomena were attributed to the excited deep and shallow trap levels and the change of recombination zone. In the Frenkel exciton model,the temperature dependence of the quantum efficiency depended on the carriers mobilities and carriers densities.The carriers mobilities increased with decreasing temperature, while the carriers densities decreased with decreasing temperature. Therefore, a peak in the curve of quantum efficiency vs. temperature was expected in the model. The high-temperature peak originated due to radiative recombination of the deep trap levels, but the low-temperature peak due to shallow ones. On the other hand, as the voltage increased, the recombination zone would be changed, which had some effects on the recombination efficiency. Some experiments proved our theoretical prediction.