共轭聚合物光电器件中痕量缺陷结构的形成机制及对光电性能影响研究

Organic conjugated polymers have been extensively studied over the past few decades, for the applications in optoelectronic devices. In order to improve the device performance (including efficiency, lifetime and stability) in advance, the structure of conjugated polymer is optimized by chemical structure, synthesis route, purification method and so on, which show much better photo- and thermal-stability than before. However the device performance of conjugated polymer is still not good enough for industrialization, which requires the degradation mechanism under device working. This project focuses on the structural evolution during device degradation would be recorded in-situ in some classic conjugated polymer like polyfluorene (PF), polythiophene (P3HT), and poly phenylene vinylene (PPV), which mainly focus on physical defects and metal/metal oxide diffused from electrodes, by the infrared and Raman spectroscopy. Advanced spectral technique of experiment and data processing would be applied in the characterization of trace chemical/physical defects in conjugated polymers qualitatively and quantitatively, to obtain low analytic limitation and high spectral sensitivity. The results would build the direct relationship between trace chemical/physical defects in conjugated polymers and optoelectronic performance in conjugated polymer based devices, which would be helpful for the advanced design, synthesis and application of conjugated polymer in optoelectronic devices, and the optimization of the device structure and fabrication processes.

有机共轭聚合物光电器件经过十余年的发展，技术已相对成熟；经过合成结构、合成路线、提纯方法等多方面的优化，目前共轭聚合物本身的纯度、光热稳定性都已经大大提高；但是还不能满足共轭聚合物光电器件产业化的要求，主要原因是共轭聚合物器件在通电和焦耳热状态下有着不同于普通光热降解的过程。本项目利用红外和拉曼光谱，原位的跟踪器件老化过程中的结构演化，重点分析在通电和焦耳热作用下，聚芴（PF）、聚噻吩（P3HT）、聚苯撑乙烯（PPV）等共轭聚合物中的物理缺陷和电极中的金属/金属氧化物杂质向活性层的扩散作用对器件结构和性能的影响。针对共轭聚合物活性层缺陷含量少、影响因素复杂，通过先进的光谱实验和后处理技术，获得高的光谱检测限和灵敏度，实现对共轭聚合物中痕量结构缺陷的定性和定量表征。研究结果将实现共轭聚合物真实的应用结构与光电性能的直接关联，对于指导新材料的设计合成与器件结构工艺的优化有重要意义。

与无机半导体材料一样，有机半导体材料中痕量的物理和化学缺陷结构对于光电性能有非常重要的影响。本项目搭建了利用拉曼光谱原位观测器件降解过程的平台，并与多种光谱、器件等表征手段相互配合，针对PF和PPV体系中的物理和化学缺陷展开研究，取得了如下主要结果：1，发现了螺芴中的excimer结构，并使用不良溶剂诱导特殊聚集体实现了对excimer拖尾发射的有效抑制，对于从加工工艺角度进一步提高螺芴衍生物的光电稳定性有重要意义。2，发现了苯基取代PPV中独特的六元环缺陷，揭示了苯基取代的特殊性，对于解决P-PPV稳定性问题有重要的意义。3，利用发光层痕量掺杂传输层材料的办法，定量研究了界面扩散效应对于光电性能的影响。以上研究大大加深了对原有有机共轭分子物理和化学结构的理解，在很多经典体系的结论改变了人们原有对体系的认识，为进一步优化溶液加工型有机光电材料结构和器件实验条件奠定了良好基础。