【摘要】：自從OLED及QD-LED提出以來,因其在能源消耗、顯示質(zhì)量、低成本以及輕便等特點,所以已經(jīng)成為顯示領域研究的熱點。本文以研究OLED及QD-LED中的工作機制為目的,從器件的結(jié)構(gòu)及材料特性出發(fā),基于載流子注入及能量傳遞理論,對基于FIrpic的藍光OLED中的激子淬滅機制進行了深入的研究,并對QD-LED的工作機制及界面處激子的淬滅進行了調(diào)控,最終改善了器件性能。針對于OLED,我們著重于磷光器件的研究。我們知道,小分子磷光材料的發(fā)明及其成功的在OLED的引入,使得器件效率得到了大幅度的提高,理論上其可實現(xiàn)100%的內(nèi)量子效率。但是,其一個顯著的缺點是高電流密度下的載流子淬滅過程。這一淬滅過程發(fā)生的幾率與載流子密度的平方成正比。其極大的限制了器件的性能,使得器件具有高的效率滾降。而且,磷光材料在OLED中需要利用合適的材料作為母體,其本身作為摻雜劑。這一摻雜過程增加了器件的制備成本,降低了器件的良率,限制了OLED的商業(yè)化進程。這里,我們針對于藍光磷光FIrpic材料進行了詳細研究。通過改變FIrpic在CBP母體中的摻雜濃度,研究了器件效率及效率滾降隨摻雜濃度變化的關系。我們驚奇的發(fā)現(xiàn),基于FIrpic的藍光器件的效率對摻雜濃度有著很低的依賴特性。即使利用純的FIrpic作為發(fā)光層,其發(fā)光效率也達到了7.76cd/A。在量子點電致發(fā)光器件方面,我們研究了QD-LED器件的發(fā)光機制。我們知道對于倒置類型的有機/無機雜化的QD-LED的發(fā)光機制為電荷的直接注入方式�；谶@一結(jié)論,我們著重對器件的空穴傳輸特性進行了研究與設計。首先設計出了既有利于空穴傳輸與注入,又有效的降低了空穴載流子對量子點中激子的淬滅幾率的階梯式結(jié)構(gòu)的空穴傳輸層,大大的提高了器件的電流效率。我們制備了結(jié)構(gòu)為ITO/Zn O/QDs/m CP/CBP/Mo O3/Al的QD-LED。由于CBP與m CP的HOMO能級存在勢壘,使得由Mo O3注入的空穴在CBP/m CP界面有一定的積累。這就在很大程度上避免了空穴在m CP/QDs界面的聚集,減少了空穴載流子對量子點中激子的淬滅。大大的提高了器件的發(fā)光效率。同時,由于激子淬滅過程的抑制,使得器件的效率滾降也有很大的降低。另外,通過利用乙醇對PEDOT:PSS空穴注入層的處理,使得該層的導電性能得到改善,增加了空穴的注入效率,提高了器件的光電性能。最后,由于高反射金屬電極的存在,使得從量子點發(fā)出的光在金屬電極處發(fā)生反射,反射的光場在器件之中形成駐波場,這一光場對量子點中的激子動力學過程有著很大的影響。通過對倒置器件中的光場分布分析,我們研究了光場對激子動力學過程的影響,并通過合理設計器件結(jié)構(gòu),有效的提高了器件效率,降低了器件效率滾降。
[Abstract]:Since OLED and QD-LED were proposed, they have become the focus of research in the field of display because of their characteristics of energy consumption, display quality, low cost and portability. In order to study the working mechanism of OLED and QD-LED, based on the theory of carrier injection and energy transfer, the exciton quenching mechanism in blue-light OLED based on FIrpic is studied in this paper, based on the structure and material characteristics of the device, and based on the theory of carrier injection and energy transfer, the mechanism of exciton quenching in blue-light OLED based on FIrpic is studied. The working mechanism of QD-LED and the quenching of excitons at the interface are regulated and the performance of the device is improved. We focus on phosphorescence devices for OLED,. We know that the invention of small molecule phosphorescent material and its successful introduction into OLED have greatly improved the device efficiency and theoretically it can achieve 100% internal quantum efficiency. However, a significant drawback is the carrier quenching process at high current density. The probability of this quenching process is proportional to the square of carrier density. It greatly limits the performance of the device and makes the device roll down with high efficiency. Moreover, phosphorescence materials need to be used as parent materials and dopants in OLED. This doping process increases the fabrication cost of the device, reduces the yield of the device, and limits the commercialization process of OLED. Here, we study the blue phosphorescence FIrpic materials in detail. By changing the doping concentration of FIrpic in the CBP matrix, the relationship between the device efficiency and the efficiency roll down with the doping concentration is studied. We are surprised to find that the efficiency of blue light devices based on FIrpic is very low dependent on doping concentration. Even if the pure FIrpic is used as the luminescent layer, the luminescence efficiency is up to 7.76 cdr / A. In the aspect of quantum dot electroluminescent devices, we study the luminescence mechanism of QD-LED devices. We know that the photoluminescence mechanism of the inverted organic / inorganic hybrid QD-LED is a direct charge injection. Based on this conclusion, we focus on the hole transmission characteristics of the device. At first, the hole transport layer with step structure is designed, which is not only favorable for hole transmission and injection, but also effectively reduces the probability of quenching excitons in quantum dots, which greatly improves the current efficiency of the device. We have prepared QD-LED. with ITO/Zn O/QDs/m CP/CBP/Mo O3/Al structure. Due to the existence of potential barriers in the HOMO energy levels of CBP and m CP, the holes implanted by Mo O 3 have a certain accumulation at the interface of CBP/m CP. This greatly avoids the accumulation of holes at the m CP/QDs interface and reduces the quenching of excitons in quantum dots by hole carriers. The luminous efficiency of the device is greatly improved. At the same time, due to the suppression of exciton quenching process, the efficiency roll drop of the device is also greatly reduced. In addition, by using ethanol to treat the PEDOT:PSS hole injection layer, the conductivity of the layer is improved, the hole injection efficiency is increased, and the photoelectric performance of the device is improved. Finally, due to the existence of high reflective metal electrode, the light emitted from quantum dots is reflected at the metal electrode, and the reflected light field forms a standing wave field in the device. This field has a great influence on the exciton dynamics in quantum dots. Through the analysis of the optical field distribution in the inverted device, we study the effect of the light field on the exciton dynamics process, and through the reasonable design of the device structure, the device efficiency is effectively improved and the device efficiency roll down is reduced.
【學位授予單位】：吉林大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN383.1

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本文編號：2357763