| 摘要: | 本論文首先研究量子點發光二極體 (Quantum Dot Light-Emitting Diode，QLED) ，透過材料調變和厚度設計，平衡電子和電洞流的復合以實現高效率發光，並研究QLED在垂直發光電晶體 (Vertical Light-Emitting Transistor，VLET) 的應用。
在優化QLED的研究中，組合(1) 三氧化鉬 (MoO3)、(2) 聚[N,N′-雙(4-丁基苯基)-N,N′-雙(苯基)-聯苯胺] (Poly-TPD)、(3) 聚（9-乙烯基咔唑） (PVK)，達到電洞層注入效果，以及利用不同混合比例的乙醯丙酮鋅 (Zn(acac)2‧xH2O) 與聚乙烯亞胺 (PEI) 形成電子注入層，實現QLED的優化。結果顯示，透過PEI優化的電子注入層，QLED外部量子效率 (External Quantum Efficiency，EQE) 可由0.025%提升100倍以上達到2.56%。進一步比較單載子電子元件特性，可確定電子相較於電洞易注入到量子點 (Quantum Dot，QD)，但電子會侷限在QD或PVK之介面，使電洞流主導QLED的電流和發光。混合PEI造成效率提升可歸因於有效降低電子注入層導電度及有效阻擋電洞流，改善電子和電洞流的平衡和復合發光。此外，亦能幫助電子注入至PVK處形成激子，再通過螢光共振能量轉移 (Fluorescence Resonance Energy Transfer，FRET) QD內部進行復合發光。
最後，將QLED與氧化鋅 (ZnO) 電晶體整合製作成VLET，此電晶體架構透過PEI調變電子注入層也能有效控制電子流由下方ZnO 電晶體注入至上方的QLED。優化的VLET元件相較於QLED元件具有更高的EQE，可達到3.04%，同時具有高亮度、高開/關比、微型化元件面積和降低功耗的優點，可實現微型顯示器和照明應用。;In the paper, the Quantum Dot Light-Emitting Diodes (QLEDs) were optimized by designing materials and layer thicknesses to balance the electron- hole recombination to achieve high emission efficiency. The QLED were then applied to develop the Vertical Light-Emitting Transistors (VLETs).
In the research of optimizing QLED, the Molybdenum trioxide (MoO3), Poly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)-benzidine] (Poly-TPD), and Poly(9-vinylcarbazole) (PVK) were used to achieve the effective injection and transport of the holes. Also, different weight ratios of Zinc acetylacetonate hydrate (Zn(acac)2‧xH2O) and Polyetherimide (PEI) were blended to modify electron injection layer. The experimental results show that with the PEI-optimized electron injection layer, the external quantum efficiency (EQE) of QLED can be increased by a factor of 100% from 0.025% to 2.56%. Further comparing the characteristics of the electron-only device, it can be determined that electrons are easier to inject into the Quantum Dot (QD) than holes. However, the electrons are mainly confined in the QD or at the PVK interface, so that the hole current dominates the current and emission of the QLED. The enhanced efficiency caused by the blend PEI could be attributed to effectively reducing the conductivity of the electron injection layer and effectively blocking the hole current, which improves the balance of the electron and hole current for recombination . In addition, PEI also facilitates the electron injection into the PVK to form the excitons, then undergoing Fluorescence Resonance Energy Transfer (FRET) to emit light from QD.
Eventually, the QLED was integrated with the ZnO transistor to complete VLET. Blending PEI in the electron injection layer is effective to control injection of electron current form the bottom ZnO transistor to the top QLED. The optimized VLET shows the EQE of up to 3.04%, even higher than the QLED. It also has the advantages of high brightness, high on/off current ratio, the miniaturized area, and reduced power consumption, which enables miniaturized displays and lighting applications. |
