有机光电器件界面分子取向调控与光电转换特性研究

Organic conjugated semiconductors have been attracting an amount of interests for their opto-electronic properties over the last two decades and are currently exploited in a large range of applications such as light-emitting diodes, photovoltaic devices, or sensors. Albeit organic-based devices have already penetrated into the market, especially in the field of flat-panel displays, solid-state lighting and renewable energy sources, intense research efforts are still carried out at both the academic and industrial level in order to better understand the key electronic processes governing the operation and performance of the devices and provide new guidelines for material design and device architecture. Organic conjugated semiconductors are composed of planar or linear molecules bound by weak intermolecular interactions, and each molecule has specific characteristics as a single molecule, such as electronic structures, absorption and emission spectra due to the molecular anisotropy in geometry. Since it is the microscopic view of chemistry that supports the device physics in organic semiconductors, the detailed investigation of molecular states such as molecular orientation and ordering, interfacial electronic structures and energy level alignment is very important for explaining the relationship between the chemical characteristics of single molecules and the physical properties of organic optoelectronic devices. As a result, controlling the molecular orientation offers a feasible way to modifying the interface energetics and thus energy transfer process at organic interfaces of organic optoelectronics. This will help build reliable fundamentals of organic devices for the further improvement of their improvement. In this project, we aim to elucidate the physical basis of the correlation between molecular orientation and electronic structures at the organic interfaces used in organic optoelectronics, focusing on the influence of molecular orientations on the interfacial energetics and the photovoltaic conversion. In particular, we will provide physical insights for exploring new structures on optical coupling, energy transfer and charge transport process for organic photovoltaic cells through the pathway of molecular orientation-dependent energy level alignment. We will make high efficiency organic photovoltaic devices based on molecular orientation engineering. We expect this project will provide not only a detailed understanding of the impact of molecular orientation in organic devices, but also a new degree of freedom in device design and fabrication.

有机光电器件中有机共轭分子结构的非对称性导致局域电子态和光电特性的各向异性，但界面分子取向对器件光电转换过程的影响规律尚缺乏深入认识，严重制约了有机光电器件的进一步发展。本项目将充分利用已有研究基础，以有机光电器件界面分子取向调控研究为着眼点，从器件物理与结构设计角度进行深入系统的研究。以原位光电子能谱、同步辐射X射线吸收谱等表界面技术为重要研究手段，重点研究有机光伏电池关键界面分子取向的控制及其对局域电子态和光电转换过程的影响，探索分子取向与光学耦合、能量传递、激子分离、电荷转移过程的构效关系及功能调控的物理机制，发展基于分子取向控制的光电转换调控新方法，获取高效有机光伏电池，实现转换效率的进一步提升，力争在有机光电器件所涉及器件结构、工作机理、加工工艺等关键物理与技术问题上有所突破，为促进有机光电器件的实际应用提供理论和技术指导。

有机光电器件，特别是有机光伏电池(OPV)的界面特性控制着光电转换过程，对器件性能有着至关重要的影响。需要继续深入探索界面特性对光电转换过程的影响规律，并在此基础上发展界面功能调控和器件性能优化的新方法，将会有助于有机光电材料和器件的完善，加速其实际应用。本项目充分利用已有研究基础，以有机光电器件界面分子取向调控研究为着眼点，从器件物理与结构设计角度进行深入系统的研究。以原位光电子能谱等表界面技术为重要研究手段，重点研究有机光伏电池关键界面分子取向的控制及其对局域电子态和光电转换过程的影响，发展了基于软纳米压印仿生微纳结构的大面积、低成本、宽光谱、广视角的光学耦合调控新方法，考察了不同体系给体-受体的器件光电特性。通过不同的分析方法理论模拟对高效光耦合结构的有机光电器件进行设计，实现了有机光电器件的光电性能的调控和优化。研制出了第三方认证光电转化效率超过13%的单结聚合物OPV（经国家太阳能光伏产品质量监督检验中心测试，检测报告编号：2017DMC00001），超过预期研究目标。上述创新型的工作，为进一步提升有机光伏电池的转换效率提供了新途径。在本项目的资助下，累计在AM、AEM、AFM、ACS Nano等发表SCI论文38篇，其中影响因子>10的论文11篇，7篇论文被遴选为期刊封面；申请中国发明专利7项。这些研究成果引起了国际同行科学家的广泛关注和肯定，多篇论文被Materials Views网站、X-MOL化学资讯平台等亮点专题报道。相关成果获得2018年江苏省科学技术奖一等奖（排名第1）、2017年教育部自然科学二等奖（排名第1）。培养研究生8名。