有机金属卤素钙钛矿发光二极管老化机制研究及器件优化

Organometallic halide perovskite light emitting diodes (PeLEDs) have been truly spectacular in recently years. However, outstanding challenges in long-term stability and degradation process remain, hampering their development and industrialization. In this project, the issues of device degradation and stability optimization of PeLEDs will be systematically investigated. We will focus on the effects of the grain boundaries, the electric field, and the self-luminescence on the stability of PeLEDs. To explore the physical degradation mechanisms of the PeLEDs, we will begin by identifying dynamics of the basic process during the device degradation, which includes the changes in charge trapping, carrier transport and recombination, decay of excited states and trap states. Furthermore, the techniques of device anatomy and recovery will be utilized to investigate and analysis the role of the functional layers on the device degradation, and the underlying mechanisms of grain boundaries, the electric field, and the self-luminescence on device degradation. Based on the above investigations, a novel perovskite/polymer composite emission layer will be constructed, incorporating with the interface modification to achieve highly efficient and stable PeLEDs. This project will create theoretical and technical innovations in the mechanisms governing the device degradation and the methods for constructing highly stable devices, respectively, which will lay the theoretical and technical foundations for the development of highly efficient and stable PeLEDs.

有机金属卤素钙钛矿发光二极管（PeLEDs）存在严重老化问题，限制了其进一步发展及工业化。本项目拟针对PeLEDs的老化机制及稳定优化开展研究，重点关注晶界、电场及自身发光对器件稳定性的影响，研究器件老化过程中电荷俘获、载流子传输与复合、激发态衰减、陷阱态等的变化，挖掘晶界、电场及自身发光对器件老化的物理机制；采用器件“解剖”和“复原”技术探索各功能层对器件老化的影响方式及范围，分析晶界、电场及自身发光对器件老化的内在作用机制；基于以上研究，构建钙钛矿/聚合物复合发光层，并结合界面修饰，获得高效稳定的PeLEDs。本项目将在PeLED器件老化机制及其改进方面取得理论及技术创新，为发展高效稳定的PeLED打下理论和技术基础。

钙钛矿发光二极管（PeLEDs）具有带隙可调，色纯度高，制备成本低的特点。但为了进一步工业化应用，需要解决其严重的老化问题。对照项目书中的研究目标，我们完成了钙钛矿发光材料的制备及发光二极管效率和稳定性的研究。本项目首先重点针对钙钛矿中高浓度的缺陷问题，优化钙钛矿材料的稳定性，减少非辐射组合造成的器件性能衰减。之后，针对PeLEDs的老化机制及稳定优化开展研究，为了提升器件的稳定性，从钙钛矿薄膜本身及界面层两个方面优化了器件稳定性。在钙钛矿薄膜方面，使用协同反溶剂和溶剂工程，提升薄膜的致密性，将钙钛矿发光二极管效率提高了两倍以上；分析薄膜形貌，界面电荷积累对器件老化的内在作用机制；使用器件“解剖”技术研究器件衰减过程中薄膜的PL衰减，抑制钙钛矿薄膜老化对器件稳定性的影响，研究器件老化过程中电荷俘获、载流子传输与复合的变化。针对空穴注入层和钙钛矿发光层界面，改善界面的能级匹配，提高空穴注入，并提高了钙钛矿的薄膜质量，进而提升器件稳定性。本项目在三维、二维PeLED器件老化机制及其改进方面取得进展，为进一步钙钛矿发光二极管老化研究打下理论和技术基础。