Physics and Applications of Doping in Molecular Semiconductor Films

技术：该项目涉及有机半导体材料的基本问题；掺杂剂的选择；掺杂对分子膜和界面的电学行为的影响；以及与器件性能特别相关的掺杂的特征。该方法包括：寻找有机金属“三明治”类型的强还原剂。据预测，含铬或含铁的有机金属化合物，如Fe(C5H5)(C6Me6)，其电离能比迄今研究过的最强分子n掺杂的电离能小200-300 meV。同样，还将研究过渡金属二硫杂环戊烯系列中的强氧化剂和过渡金属氧化物，以及作为操作条件(温度、环境)的函数的掺杂剂相对于扩散或污染的稳定性。在第二个研究领域，将讨论界面掺杂与界面工程(电极修饰)在载流子注入方面的相对优势。将评估掺杂对块状薄膜中载流子迁移率的影响，以及掺杂引起的填充深陷阱的好处是否超过这些杂质造成的额外散射和陷阱。扫描隧道显微镜/光谱学(STM/STS)将被用来研究分子分辨的掺杂和相关的电势。这项研究的第三个总主题，掺杂在器件中的应用，将涉及到研究两边掺杂的有机光伏电池的功率转换效率，即p掺杂施主和n掺杂受主层，以改善载流子提取、接触和电子-空穴对分离。还将研究使用过渡金属氧化物分子(作为掺杂剂)和薄膜(作为高功函数电极)作为电荷产生层和高效率多层叠层器件的关键结构。这些活动将涉及一种多技术方法，以充分描述这些材料的电子、化学和电荷传输特性(紫外线、X射线和反向光电子能谱、扫描隧道显微镜/扫描隧道显微镜、电流和电容-电压测量)。建立了与化学家、设备物理学家和理论家的合作，这将是研究方法的一个组成部分。非技术性：该项目解决与技术高度相关的电子/光子学材料科学的基础研究问题，并将为学生培训提供重要机会。该项目有望提高我们的理解，促进化学掺杂在有机器件中的推广，具有潜在的重要工业应用价值。它将使学生(研究生和本科生)接触到一系列基本材料物理和电子结构问题，以及实际设备问题，各种实验技术，并通过化学和电子结构理论的合作，接触不同的研究环境。通过参加普林斯顿大学的外展项目、向工业界提供的短期课程以及参与科学协会，PI一直并将继续非常积极地教授和传播有机电子领域的知识。

Technical: This project addresses fundamental issues in organic semiconductor materials; dopant selection, impact of doping on the electrical behavior of molecular films and interfaces, and features of doping particularly relevant to device performance. The approach encompasses: a search for strongly reducing agents of the organometallic 'sandwich' type. Cr- or Fe-based organometallics such as Fe(C5H5)(C6Me6) are predicted to have an ionization energy 200-300 meV smaller than the strongest molecular n-dopant investigated to date. Similarly, strongly oxidizing agents in the transition metal dithiolene family and transition metal oxides will be studied, along with the stability of the dopant vs. diffusion or contamination as a function of operating conditions (temperature, environment). In the second area of research the relative benefits of interface doping vs. interface engineering (electrode modification) in terms of carrier injection will be addressed. The impact of doping on the mobility of carriers in bulk films, and whether the benefit of doping-induced filling deep traps outweighs additional scattering and trapping caused by these impurities will be assessed. Scanning tunneling microscopy/ spectroscopy (STM/STS) will be used to investigate dopants and related potentials with molecular resolution. The third general theme of the research, application of doping to devices, will involve investigation of power conversion efficiencies in organic photovoltaic cells doped on both sides, i.e., p-doped donor and n-doped acceptor layers, to improve carrier extraction, contacts and electron-hole pair separation. The use of transition metal oxide molecules (as dopants) and films (as high work function electrodes) for charge generation layers and key structures of high efficiency, multi-layer stacked devices will also be studied. These activities will involve a multi-technique approach to fully characterize the electronic, chemical and charge transport properties of these materials (ultra-violet, X-ray and inverse photoemission spectroscopy, STM/STS, current- and capacitance-voltage measurements). Collaborations with chemists, device physicists and theoreticians are established, and will be an integral feature of the research approach.Non-technical: The project addresses basic research issues in electronics/photonics materials science with high technological relevance, and will provide important opportunities for student training. The project is expected to improve our understanding and facilitate the generalization of chemical doping in organic devices, with potentially important industrial applications. It will expose students (graduate and undergraduate) to a range of fundamental materials physics and electronic structure problems, as well as to practical device issues, to a variety of experimental techniques, and to different research environments through collaborations in chemistry and theory of electronic structure. Through his participation in outreach programs at Princeton University, short courses given to industry, and involvement in scientific societies, the PI has been and will remain extremely active in the teaching and dissemination of knowledge in the field of organic electronics.