蓝、白光顶发射有机发光二极管中的微腔效应研究及器件高性能化

发布时间：2018-07-03 16:58

本文选题：有机发光二极管 + 顶发射　；参考：《南京邮电大学》2015年博士论文

【摘要】：顶发射有机发光二极管(Top-emitting organic light-emitting diode,TEOLED),以其分辨率高、开口率大和衬底选择灵活等优势在有机平板显示领域,尤其是微显示领域受到广泛关注。然而,TEOLED中的光学微腔效应严重抑制了器件的发光强度和色纯度,其对蓝色和白色TEOLED的影响尤其严重,造成了蓝、白光TEOLED制备困难,并严重影响了器件性能。因此,开展TEOLED中微腔效应的研究工作,有效设计与调控微腔对于成功制备高性能蓝、白光TEOLED至关重要。本文首先将电偶极子理论和传输矩阵理论相结合改进了微腔效应的理论模型,并与实验相结合研究了微腔效应对于蓝光TEOLED的影响,设计了优化的器件结构,有效增强了蓝光强度并改善了蓝光的色饱和度;在此基础上,对白光TEOLED进行了一系列的设计和优化,提高了白光中蓝光的比例,改善了顶发射白光的效率和色纯度。研究工作主要包括以下几个方面:(1)采用电偶极子辐射的经典电磁理论分析激子的辐射模式,将偶极矩的取向和辐射电磁波的偏振等因素纳入辐射模式的计算中,使理论模型更加完善。采用传输矩阵理论分析光波在多层膜系中的传输,将多膜层结构的TEOLED等效为单层结构,结合偶极子辐射模式,研究TEOLED中微腔共振效应对激子辐射的影响。运用该理论模型,可以从理论上比较准确地计算TEOLED的微腔共振光谱、发光光谱,并进而计算色坐标、色温、显色指数等器件的色度参数。(2)常规TEOLED中的微腔共振效应抑制了蓝光的出射,使蓝光的效率和色度都比较差。为了改善蓝光TEOLED的性能,本文引入了“金属/Ag”双层阴极结构,增强电子的注入效率和蓝光耦合输出效率。首先计算了金属材料的折射率实部和虚部对双层阴极反射率和反射相位的影响,确定“钐/Ag(Sm/Ag)”双层阴极结构能实现较低的反射。然后计算了不同Sm、Ag厚度对蓝光TEOLED光谱和色坐标的影响,发现减小Ag厚度,增加Sm厚度有利于改善蓝光色纯度。最后,制备了具有不同Sm/Ag双层阴极的蓝光TEOLED,验证了理论计算的结果,同时改善了顶发射蓝光的色纯度。最优化蓝光TEOLED的光谱接近蓝光材料本征光谱,而且器件在0-75°视角范围内光谱几乎没有变化,实现了很好的色纯度和角度稳定性。(3)TEOLED中微腔效应对蓝光的抑制使顶发射白光中蓝光的强度不够,白光色度偏红。本文利用微腔效应中的多光束干涉增强蓝光输出强度,改善顶发射白光色度。首先,理论计算了具有不同空穴传输层(NPB)厚度TEOLED的微腔共振波长,并制备了相应器件验证理论计算结果。理论和实验结果表明,当NPB厚度为100 nm时,微腔的共振波长与蓝光比较匹配,器件中的蓝光输出较强,能与红光混合获得比较平衡的白光。接着,通过在红光和蓝光层之间插入载流子/激子阻挡层,稳定了主体材料CBP中的激子复合区域,使白光在不同电压下的色漂移减弱,改善了白光的稳定性。(4)微腔效应中的干涉过程分为多光束干涉和宽角干涉。本文对白光TEOLED中的宽角干涉因子和多光束干涉因子分别进行了计算和分析,以提高器件的效率和色度。首先计算了TEOLED中电极和激子位置对多光束干涉、宽角干涉强度的影响,发现增强阳极反射并减弱阴极反射可以减弱多光束干涉,而使发光激子靠近阳极可以增强宽角干涉,均能增强器件中的蓝光输出。接着,从实验上制备了高反射阳极和低反射阴极的白光TEOLED,并在此基础上,利用δ掺杂器件和蓝/红、红/蓝结构的白光TEOLED重点研究了宽角干涉对顶发射白光性能的影响,并利用宽角干涉进一步增强蓝光输出。最终得到的白光TEOLED效率高于具有相同有机层结构的底发射器件,同时色度更加接近标准白光。(5)在白光TEOLED中,引入异质结结构的双蓝光发光层,使激子复合区域位于蓝光层内,有效提高了蓝光的发光强度。为了优化白光的色纯度和稳定性,对发光层中激子的行为进行了研究。首先制备单载流子器件研究客体的载流子传输行为,发现蓝光客体充当空穴传输通道和电子陷阱,而红光客体则充当电子传输通道和空穴陷阱,其中红光客体的陷阱效应对低压下的红光强度有贡献;然后利用δ掺杂器件研究激子的分布,确定了激子在主体材料SPPO1中的扩散长度,由此确定了蓝光和红光层的厚度;接着利用阻隔层研究了蓝、红客体之间的能量转移,发现存在较弱的Dexter能量转移,有助于提高白光的稳定性。根据以上研究结果,设计了优化的白光TEOLED结构,获得了高效、稳定的顶发射白光,效率为13.3cd/A,在10-104 cd/m2亮度范围内,色坐标漂移仅(0.009,0.001)。最后从激子扩散、能量转移和陷阱效应等方面对器件的稳定性机制进行了深入的分析。
[Abstract]:The top emission organic light-emitting diode (Top-emitting organic light-emitting diode, TEOLED), with its high resolution, high opening rate and flexible substrate selection, has been widely concerned in the field of organic plate display, especially in the field of micro display. However, the optical microcavity effect in TEOLED seriously inhibits the light intensity and color purity of the device. The effect on blue and white TEOLED is especially serious, which causes the difficulty in the preparation of blue and white TEOLED, and seriously affects the performance of the device. Therefore, it is important to design and regulate the microcavity effect in TEOLED for the successful preparation of the high performance blue, the white light TEOLED to the gate. Combining with the theory, the theoretical model of microcavity effect is improved, and the effect of microcavity effect on blue light TEOLED is studied in combination with the experiment. The optimized device structure is designed, the blue light intensity is enhanced and the color saturation of blue light is improved. On this basis, a series of white light TEOLED is designed and optimized, and white light is improved. The proportion of blue light improves the efficiency and color purity of the top emitting white light. The research work mainly includes the following aspects: (1) the classical electromagnetic theory of electric dipole radiation is used to analyze the radiation pattern of the exciton, and the orientation of the dipole moment and the polarization of the radiation electromagnetic wave are incorporated into the calculation of the radiation mode, which makes the theoretical model more perfect. The transmission matrix theory is used to analyze the transmission of light wave in the multilayer film system, the TEOLED of the multi layer structure is equivalent to a single layer structure, and the effect of the resonance effect on the exciton radiation in TEOLED is studied by the dipole radiation mode. The theoretical model is used to calculate the microcavity resonance spectra and luminous light of TEOLED theoretically. The chromaticity parameters of the devices such as color coordinates, color temperature and color index are calculated. (2) the micro cavity resonance effect in conventional TEOLED inhibits the emission of blue light and makes the efficiency and chromaticity of blue light relatively poor. In order to improve the performance of blue light TEOLED, this paper introduces a "metal /Ag" double layer cathode structure to enhance the injection efficiency of the electron and Lan Guangou. The effect of the refractive index and the imaginary part of the metal material on the reflectivity and the reflection phase of the double cathode is calculated. The "SM /Ag (Sm/Ag)" double layer cathode structure can be determined to achieve a lower reflection. Then the effects of different Sm and Ag thickness on the blue light TEOLED spectrum and the color coordinates are calculated, and the thickness of Ag and the thickness of the Sm can be reduced. It is beneficial to improve the blue color purity. Finally, the blue light TEOLED with different Sm/Ag double layer cathodes is prepared. The result of the theoretical calculation is verified, and the color purity of the top emitting blue light is improved. The optimized blue light TEOLED spectrum is close to the intrinsic spectrum of the blue light material, and the device has almost no change in the spectrum within the range of 0-75 degrees. Good color purity and angle stability. (3) the inhibition of the microcavity effect on blue light in TEOLED makes the top emitting Bai Guangzhong blue light not strong enough and the white color is red. This paper uses the multi beam interference in the microcavity effect to enhance the blue light output intensity and improve the top emission white light chromaticity. First, the thickness of the different cavity transport layer (NPB) is calculated theoretically. The resonance wavelengths of the microcavity of TEOLED and the theoretical results of the corresponding device verification are prepared. The theoretical and experimental results show that when the thickness of NPB is 100 nm, the resonant wavelength of the microcavity is matched with the blue light, the blue light output in the device is stronger and the white light can be more balanced with the red light. Then, the load is inserted between the red and blue light layers. The flow sub / exciton barrier layer stabilizes the exciton complex region in the main material CBP, which reduces the color drift of the white light at different voltages and improves the stability of the white light. (4) the interference processes in the microcavity effect are divided into multi beam interference and wide angle interference. The wide-angle interference factors and multi beam interference factors in the white light TEOLED are respectively carried out in this paper. It is calculated and analyzed to improve the efficiency and chromaticity of the device. First, the influence of the electrode and exciton position in the TEOLED on the interference of multi beam and wide angle interference is calculated. It is found that the enhanced anode reflection and the weakening of the cathode reflection can weaken the multi beam interference, and the light exciton near the anode can enhance the wide angle interference, which can both enhance the device. The white light TEOLED with high reflection anode and low reflection cathode was prepared experimentally, and on this basis, the effect of wide angle interference on the white light performance of the top emission was studied with delta doping and blue / red, red / Blue structure of white light TEOLED, and the blue light output was further enhanced by wide angle interference. The final white light was obtained. The TEOLED efficiency is higher than that of the bottom emitting devices with the same organic structure, and the chromaticity is closer to the standard white light. (5) in the white light TEOLED, the double blue light layer of heterostructure is introduced to make the complex region of the exciton in the blue light layer, and the luminescence intensity of the blue light is improved effectively. In order to optimize the color purity and stability of white light, the luminescent layer is optimized. The behavior of the exciton is studied. First, single carrier device is prepared to study the carrier transport behavior of the object, and the blue object acts as the hole transmission channel and the electron trap, while the red object acts as the electron transport channel and the hole trap, in which the trap efficiency of the red light object contributes to the red light intensity under the low pressure; then the use of the red light object is used. The distribution of the exciton is studied by the delta doped device, the diffusion length of the exciton in the main material SPPO1 is determined, and the thickness of the blue and red light layers is determined. Then the energy transfer between blue and red objects is studied by the barrier layer, and the weak Dexter energy transfer is found to help to improve the stability of the white light. Based on the above results, The optimized white light TEOLED structure has been designed to obtain high efficiency, stable top emission white light, and the efficiency is 13.3cd/A. The color coordinate drift is only (0.009,0.001) in the 10-104 cd/m2 luminance range. Finally, the stability mechanism of the device is deeply analyzed from the exciton diffusion, the energy transfer and the trap effect.
【学位授予单位】：南京邮电大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN383.1

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