【作者】 张秀龙；

【导师】 杨盛谊；

【作者基本信息】 北京交通大学 ， 光学， 2007， 硕士

【摘要】 有机电致发光器件(OLED)由于其在大面积平板显示领域的潜在应用价值,引起了人们的广泛关注。但是,仍然有一些问题亟待解决,电致发光机理还不完善,界面问题仍需进一步研究。本文利用常规的光电测试方法并结合交流阻抗谱方法,对有机电致发光器件中载流子输运理论、器件界面光电特性等问题进行了系统的研究。首先,利用常规的光电测试方法,对单层电致发光器件ITO/Alq3(90nm)/Al的载流子注入与传输机制进行探讨。实验结果表明,载流子输运机制为陷阱电荷限制电流;根据低压下的线性电流-电压特性,可知有机层与金属电极的界面接触特性为欧姆接触。其次,利用交流阻抗谱方法,进一步研究了ITO/Alq3(90nm)/Al的电学特性,证明了有机层与金属电极的界面接触特性为欧姆接触;由器件的交流阻抗谱得到了器件的等效电路模型,该器件可看作是由电阻RP和电容CP并联再与电阻RS串联而成的,并根据实验数据求出了RP、CP和RS的数值;进一步,我们研究了器件的阻抗-电压、电容-电压以及电容-频率的变化规律,指出器件的载流子传导机制为指数分布式的陷阱电荷限制电流,有机层的介电弛豫时间随所加电压的增加而减小。最后,利用常规的光电测试方法,研究了有机异质结界面的电致发光和光致发光特性。通过比较各种光谱,实验结果证明基于TPD/PBD的异质结器件中形成激基复合物的分子类型为(TPD*PBD),并且是在TPD分子和PBD分子的交界面处形成的,在不同的器件中均观察到了TPD分子的荧光发射;根据激基复合物的发光特性,我们提出了增强激基复合物的发光的两种途径,即混合蒸镀过渡层的方法和类量子阱器件结构,并对二者的发光机理进行了讨论。更多还原

【Abstract】 Organic light-emitting diodes (OLEDs) have attracted considerable attention due to their diverse promising applications in large-area flat panel displays. However, there are still many problems to be solved, and the charge transport mechanism is not clear and its interface properties need to be further investigated.In this dissertation, by using traditional measurement methods and AC impedance spectroscopy technique, we have systematically studied the theory of charge carriers injection and transport, and the photoelectric characteristics of the organic heterojunction interface in OLEDs.Firstly, the charge carriers injection and transport mechanism of single-layer device ITO/Alq3(90nm)/Al was investigated by using the traditionally measurement methods. Our experimental results indicated that the charge carriers conduction mechanism of ITO/Alq3(90nm)/Al is trap-charge limited current (TCLC) with exponential distribution. At lower voltages, the currents increase linearly with applied voltages, which implies that the organic/metal interface are ohmic.Secondly, by using impedance spectroscopy technique, the conduction mechanism of the single-layer device ITO/Alq3(90nm)/Al was further studied, a half-cycle in its AC impedance spectroscopy was observed, indicating that no schottky barriers were formed at the ITO/organic interface and organic/Al interface. According to the impedance spectroscopy of these devices, it can be interpreted in terms of an equivalent circuit model of a contact resistance Rs in series with a parallel combination of a capacitance CP and a resistance RP. According to our experimental data, the values of RP, CP and RS can be figured out. Further, we have studied the impedance-voltage (Z-V), capacitance-voltage (C-V) and capacitance-frequency (Z-ω) of the single device, and its conduction mechanism was confirmed to be trap-charge limited current with exponential distribution and the dielectric relaxation time of the organic material decreased dramatically with increasing applied voltages.Lastly, by using traditional measurement methods, we have investigated the electroluminescence (EL) and photoluminescence (PL) of the interface in organic heterostructure diodes. By comparing the EL, PL and absorption spectra of pure TPD film and pure PBD film, bilayer structure film TPD/PBD and incorporated film更多还原