表面包覆铂基磁性合金纳米粒子掺杂的有机发光二极管研究

High power efficiency is one of the key technical challenges organic light-emitting diode (OLED) faces for commercialization. Incorporation of noble metal nanoparticles (NPs) or magnetic NPs into the active organic emissive layer can help to boost the power efficiency. This is achieved through the coupling of the localized surface plasmon resonance (LSPR), formed on the surface of metal NPs, with the electroluminescence within the OLED. The use of magnetic NPs is favorable for the efficient operation of OLED through effective combination of opposite charge carriers in the emissive layer. However, the presence of metal NPs and magnetic NPs can also induce exciton quenching. In this project, we intend to study the high efficiency OLEDs using carbon-coated core/shell NPs (i.e. FePt@C, CoPt@C, NiPt@C). The carbon-coated core/shell NPs, synthesized by pyrolysis of bimetallopolymer, possess both LSPR and magnetic effects, and also enable to prevent exciton quenching. The aim of the work is to realize high efficiency OLED by optimizing NP doping into the active emissive layer. We will design and also synthesize different carbon-coated core-shelled NPs that can be solution-processed for application in OLEDs, understand the effects of sizes and concentration of NPs on exciton quenching in OLEDs, optimize the core-shell NP structures and study the performance enhancement of NP-doped OLEDs compared to a conventional control OLED through theoretical simulation and experimental optimization.

如何提高有机发光二极管(OLED)的功率效率是其市场化应用面临的关键问题之一。贵金属纳米粒子和磁性纳米粒子掺杂到OLED发光层中都可以提高功率效率，前者是通过金属纳米粒子表面激发产生的局域表面等离子体共振效应同发射能量耦合实现，后者是由于磁性纳米粒子可以加速反极性电荷载体重组，使磁性掺杂OLED的功率效率更高。本项目基于铂基双核金属聚合物经高温可控分解后生成表面碳包覆的铂基磁性合金纳米粒子（如FePt@C，CoPt@C，NiPt@C等），其中包覆层可防止激子在金属纳米颗粒表面发生淬灭，而合金纳米粒子同时具有磁效应和表面等离子体效应，将其掺杂进OLED器件发光层中，利用两者协同作用有望更有效的提高功率效率。本工作致力于研究磁性合金纳米粒子及其尺寸、掺杂浓度在OLED器件中的影响机制，并通过理论计算建立掺杂改性前后材料界面性能变化与OLED功率效率的关系模型，使得本项目具有学术和应用双重价值。

近年来，有机发光二极管由于其在平板显示、固态照明、虚拟现实等领域的极具前景的商业应用价值而受到广泛关注。然而，有机发光二极管的实际应用仍面临着可满足工业化要求的效率和器件寿命的挑战。本项目中，通过将表面碳包覆的磁性合金纳米粒子以仅仅0.5 wt ‰的低浓度掺杂到荧光OLED器件空穴传输层中，便可实现电致发光效率48.5%的提高。同时本项目深入研究了合金纳米粒子的磁性，光散射效应，局域表面等离子共振效应在OLED器件中的作用机制。研究发现，合金纳米粒子的磁性可以增加激子在总载流子中的比例以及单线态在激子中的比例，而合金纳米粒子的表面等离子体和激子耦合可以有效增加激子的产生，同时表面等离子体和激子的耦合可以有效增加束缚在波导模式中的光提取。此外，纳米粒子的散射作用可以改变由于全反射造成的束缚在波导模式中的光入射角，从而提高光提取效率。总之，本研究结果表明利用磁性合金纳米粒子制备有机/无机复合空穴传输层是一种可以有效提高OLED和其它类似发光器件的电致发光效率的途径。