非欧姆注入单层有机发光器件低场下电流传导温度特性的数值研究

温度是影响有机发光器件特性的一个重要因素,考虑了电流的注入限制和体限制之后,运用数值方法,研究了在低电场下温度对单层有机发光器件的J-V特性以及电场和载流子在有机层中的分布的影响。结果表明,在一定电压下,温度升高时,器件电流增大,有机层中载流子及其梯度分布增大,电场强度分布梯度也增大。并且当温度逐渐升高时,器件的电流传导将趋向于体限制,而当温度逐渐降低时,器件电流传导将趋向于注入限制,此时有机层内各处电场强度趋于均匀。并且结果表明,数值结果与实验结果符合得比较好。

Numerical Study of the Low-field Temperature Characteristics of the Current Conduction in Single Layer Organic Light-emitting Devices with Non-ohmic Charge Injection

Temperature plays an important role on the characteristic of the organic light-emitting devices,such as it can change the carriers mobility,and influence on the device's current,luminescence efficiency,lifetime and so on.So adequate understanding of the temperature characteristic of the organic light-emitting device is more needed and important,but the study about it is still insufficient.Sksaha,Feller and Ashok have studied the temperature characteristics of organic light-emitting devices by experimental and theoretical methods,but those works are not sufficient to adequately understand the temperature influence on the properties of organic light-emitting devices.Fowler-Nordhein tunneling and thermionic emission are the dominant mechanisms of current injection at metal/organic interfaces,and the former can be ignored at low-field,so injection current nearly equals to thermionic emission current.After taking the injection limited(IL)and bulk limited(BL)current into consideration at the same time on the condition of non-ohmic injection contact and low-field operation,using numerical methods the temperature influence on the device's J-V characteristic,the carrier density and the filed distribution in the organic layer were studied.Results show that device current will increase as the temperature increasing at a given voltage,and that the J-V characteristic curve become stepper in the higher temperature than that in the lower temperature.Carrier density and its distribution grads in organic layer will increase as the temperature increasing at a given voltage.Field distribution grads increases as the temperature increasing in the organic layer,and the current conduction will approach to be bulk limited(BL).Field distribution grads decrease as the temperature decreasing in the organic layer at a given voltage,and the field intensity through organic layer will approach to U/d,with U the bias,and d the organic film thickness,the current conduction will approach to be injection limited(IL).The results have a good agreement with the experi-mental data when using proper parameters.