Understanding the spin-entangled triplet-pair state in organic semiconductors

与牛津大学的理论家合作，该项目涉及研究有机半导体中激发态（特别是“三重态”）的基本电子行为，用于光电子学，显示器和极化电子学。您将在谢菲尔德的超快激光设施中使用超快光谱学研究模型系统（薄膜，光子器件或蛋白质结合半导体）。[[背景]]单线态裂变是一个光子产生两个激发态的过程。这种二合一机制可以显著提高太阳能电池的效率（从33%提高到>40%）。因此，有显着的学术界和工业界的兴趣，开发新的单重态裂变敏化光伏或光电应用最近。不幸的是，迄今为止没有任何材料被证明是理想的。这部分是因为对单线态裂变过程以及控制它的分子参数缺乏基本的了解。我们所知道的是单线态裂变通过一个中间激发态进行，称为（TT）：一对相关的三重态（自旋S=1激发）。单个三重态的自旋在室温下可以保持纠缠超过微秒，即使三重态分开，也使其成为一个令人兴奋的研究领域，其应用可能远远超出光子学。[[Project details]]在这个项目中，你将研究有机半导体的磁场依赖光谱学，使用超快（飞秒）光脉冲来绘制谢菲尔德超快激光设备中单线态裂变过程的电子景观。重点将是发展对三重态（TT）的理解：它们的寿命和能量;它们保持自旋相干的时间;它们移动的距离和速度。目的是了解哪些分子和薄膜参数控制这些特性，以及如何优化它们以用于各种光电和光子器件。

In collaboration with theoreticians at the University of Oxford, this project involves studying the fundamental electronic behaviour of excited states in organic semiconductors (specifically 'triplet-pair' states) for applications in photovoltaics, displays and polaritonics. You will study model systems (either thin films, photonic devices or protein-bound semiconductors) using ultrafast spectroscopy at Sheffield's ultrafast laser facility. [[Background]]Singlet fission is a process whereby one photon creates two excited states. This two-for-one mechanism could dramatically increase solar cell efficiency (from 33% to >40%). There has therefore been significant academic and industrial interest in developing new singlet fission sensitizers for photovoltaic or optoelectronic applications recently. Unfortunately, to-date no material has proved ideal. This is in part because of a fundamental lack of understanding of the singlet fission process and what molecular parameters control it. What is known is that singlet fission proceeds through an intermediate excited state, known as (TT): a correlated pair of triplets (spin S=1 excitations). The spins of the individual triplets may remain entangled over microseconds at room temperature, even as the triplets move apart, making it an exciting area of research with possible applications well beyond photovoltaics. [[Project details]]In this project you will study the magnetic-field dependent spectroscopy of organic semiconductors using ultrafast (femtosecond) pulses of light to map the electronic landscape of the singlet fission process in Sheffield's ultrafast laser facility. The emphasis will be on developing an understanding of triplet-pair states (TT): their lifetime and energetics; how long they remain spin-coherent; how far and fast they move. The aim is to understand which molecular and film parameters govern these properties and how they can be optimized for use in a variety of optoelectronic and photonic devices.