Electron dynamics at surface-modified photocathodes

表面改性光电阴极的电子动力学

• 批准号: 424936963
• 负责人: Dr. Dennis Friedrich
• 金额: --
• 依托单位: Fachgebiet Grundlagen von Energiematerialien
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/424936963?language=en
• 关键词: Electron; dynamics; surface; modified; photocathodes

This project aims to understand the fundamental processes that govern electron dynamics and energetics of prototypical photoelectrode surfaces, the associated internal interfaces near semiconductor surfaces and related model systems in view of photoelectrochemical hydrogen generation. The detailed mechanisms of interfacial electron transfer processes and their dynamics are still insufficiently understood. We propose to specifically modify the surface electronic and chemical properties of III-V compound semiconductor absorber systems to promote multi-electron processes. Time-resolved two-photon photoemission (tr-2PPE) for explicitly surface-sensitive analysis will be combined with density-functional theory (DFT)-based numerical simulations in order to gain a fundamental understanding of key electron transfer and recombination processes. Tr-2PPE is a unique technique that directly probes the kinetic energy and dynamics of photoemitted electrons accessing at the same time the electronic structure and temporal occupation of surface-near states. III-V compound semiconductors serve as relevant model systems to investigate interfacial dynamics with respect to selected surface modification procedures. Ways to modify III-V surfaces include epitaxial growth of thin films, in-situ surface transformation and catalyst deposition. These methods can produce quasi-two dimensional overlayers to slow down corrosion and enhance photocatalytic activity. The modification with such surface layers will enable tuning of the electron transfer dynamics by selective electronic structure modifications. Studying different types of surface modification will allow us to draw a general picture how interface design benefits electron transport towards the catalytically active surface. Key scientific questions are (i) if cooling of hot electrons at modified surfaces can be substantially slower than in bulk material at relevant excitation densities, (ii) if interface states can be introduced specifically near the conduction band, (iii) how electron collection can be enhanced and non-radiative recombination suppressed. In the long-term perspective of the Research Consortium, answers to these questions will benefit the design of functionalization layers of the envisaged new multi-junction absorber systems in order to provide optimum charge separation and transfer for multi-electron catalytic processes.

该项目旨在了解光电化学制氢中控制原型光电极表面的电子动力学和能量学的基本过程，半导体表面附近的相关内部界面和相关模型系统。界面电子转移过程及其动力学的详细机制仍然没有得到充分的理解。我们建议专门修改III-V族化合物半导体吸收剂系统的表面电子和化学性质，以促进多电子过程。时间分辨双光子光电发射（tr-2 PPE）明确的表面敏感分析将结合密度泛函理论（DFT）为基础的数值模拟，以获得关键的电子转移和复合过程的基本理解。Tr-2 PPE是一种独特的技术，它直接探测光发射电子的动能和动力学，同时访问表面附近状态的电子结构和时间占用。III-V族化合物半导体作为相关的模型系统，以调查界面动力学与选定的表面改性程序。III-V族表面改性的方法包括外延生长薄膜、原位表面转化和催化剂沉积。这些方法可以产生准二维覆盖层，以减缓腐蚀并增强光催化活性。用这样的表面层的改性将使得能够通过选择性的电子结构改性来调节电子转移动力学。研究不同类型的表面改性将使我们能够绘制一个一般的画面界面设计如何有利于电子传输到催化活性表面。关键的科学问题是：（i）在相关的激发密度下，热电子在改性表面的冷却是否比在体材料中慢得多，（ii）是否可以在导带附近引入界面态，（iii）如何增强电子收集和抑制非辐射复合。从研究联盟的长远角度来看，这些问题的答案将有利于设计设想的新的多结吸收剂系统的功能化层，以便为多电子催化过程提供最佳的电荷分离和转移。