Scanned-probe Characterization of Charge Generation, Recombination, and Motion in Organic Semiconductors

非技术摘要：阳光代表着一种无限的清洁能源。我们如何才能为每个人提供一种廉价的方式来捕捉和使用太阳能来运行他们的家用电器和车辆？屋顶硅基光伏电池已经存在，可以将阳光转化为电能；然而，这些电池的制造和安装成本很高。该项目的目标是研究由塑料和有机分子制成的太阳能电池，这种电池可以像油漆一样薄而便宜。塑料/有机太阳能电池材料已经被研究了很长时间，但这些材料如何在分子水平上将光转化为电能仍然知之甚少。为了更好地理解这些材料，我们正在开发一种显微镜，能够在一纳秒(十亿分之一秒)或更快的时间尺度上观察电荷在分子水平上的运动。这样的显微镜将为我们提供一种新的方法来研究分子水平的过程，从光合作用到在金属表面发生的具有重要工业意义的化学反应。由该项目资助的研究人员正在利用他们在科学仪器和计算机编程方面的知识来开发实验，向初中生介绍从音乐物理到电化学原理的各种主题。技术摘要：该项目的目标是测试分子设计规则，这些规则被认为是控制由接受电子和捐赠电子的分子制成的薄膜太阳能电池中如何将光转化为电能的规则，也就是所谓的供体-受体混合物。对具有系统变化的能级和背景电荷密度的分子制备的施主-受主共混物进行了电荷复合动力学和电荷迁移率的局域测量，以支持或驳斥描述这些混合物中太阳光产生电荷的理论。为了能够进行这些研究，开发了扫描探针显微镜测量，能够以纳秒的时间分辨率和纳米的空间分辨率来确定在施加纳秒持续时间的光脉冲后，施主-受主混合物薄膜中的自由电荷产额和随后的复合动力学。开发了一组单独的扫描探针测量，用于从近表面电场波动的测量中推断局部电荷迁移率。在这个项目中创造的工具有望最终在研究光催化和电催化等工业重要过程以及光合作用等自然重要过程中得到广泛应用。这项研究资助的研究人员正在利用他们在科学仪器和计算机编程方面的知识来开发实验，向初中生介绍从音乐物理到电化学原理的各种主题。

Nontechnical Abstract:Sunlight represents a limitless source of clean energy. How can we provide everyone with a cheap way to capture and use the sun's energy to run their appliances and vehicles? Rooftop silicon-based photovoltaic cells already exist for converting sunlight into electricity; however, these cells are expensive to manufacture and install. This project's goal is to study solar cells made from plastics and organic molecules, which could allow solar cells to be as thin and inexpensive as a coat of paint. Plastic/organic solar-cell materials have been studied for a long time, but how these materials convert light into electricity at the molecular level remains poorly understood. To better understand these materials we are developing a microscope capable of watching charge move at the molecular level on the timescale of one nanosecond (one billionth of a second) or faster. Such a microscope would give us a new way to study molecular-level processes ranging from photosynthesis to industrially important chemical reactions taking place at a metal surface. The researchers funded by this project are using their knowledge of scientific instrumentation and computer programming to develop experiments introducing middle and high school students to topics ranging from the physics of music to the principles of electrochemistry.Technical Abstract:The goal of this project is to test molecular design rules thought to govern how light is converted into electricity in thin-film solar cells made from electron-accepting and electron-donating molecules, so-called donor-acceptor blends. Localized measurements of charge recombination dynamics and charge mobility are carried out on donor-acceptor blends prepared from molecules with systematically varied energy levels and background charge density to support or refute theories describing how charge is generated from sunlight in these blends. To enable these studies, scanned-probe-microscope measurements are developed capable of determining, with nanosecond temporal resolution and nanometer spatial resolution, the free charge yield and subsequent recombination dynamics in a thin film of a donor-acceptor blend following the application of a nanosecond-duration pulse of light. A separate set of scanned-probe measurements are developed for inferring the local charge mobility from measurements of near-surface electric field fluctuations. The tools created during this project are expected to ultimately have broad applications in studying industrially important processes like photocatalysis and electrocatalysis and in naturally important processes like photosynthesis. The researchers funded by this research are using their knowledge of scientific instrumentation and computer programming to develop experiments introducing middle and high school students to topics ranging from the physics of music to the principles of electrochemistry.