Collaborative Research: Photomechanical Behavior in Photovoltaic Semiconductors

光伏半导体能够将光转化为电能。它们是太阳能电池的主要组成部分，太阳能电池从阳光中提供可再生能源。这些半导体往往以一种脆性的方式失效，限制了它们的一般用途，仅限于小规模应用。然而，新的证据表明，光伏半导体的机械行为对阳光很敏感，在光照下表现出相对延展性的潜力。这种光-机械耦合效应背后的机制仍然难以捉摸。该奖项支持基础研究，以阐明光致激发如何控制光伏半导体的机械行为。这一新知识有望为设计高度稳定和耐用的光伏器件提供策略，如太阳能电池、晶体管、发光二极管和光电探测器，为广泛的工程应用提供基础。该奖项还将为力学、材料科学和工程以及光物理等跨学科领域的研究生和本科生提供教育和培训。该奖项将通过让女性和代表性不足的少数民族参与研究活动来促进多样性。光伏半导体的光机械行为由位错和孪生等光诱导变形机制决定。在这个项目中，我们将使用一个多尺度的模拟和实验框架来精确地描述光致电子空穴激发对原型光伏半导体碲化镉中位错和缠绕机制的影响。在亚原子尺度上，将进行高级量子力学模拟，以确定电子-空穴对位错和孪晶成核能垒和势垒的影响，以及位错的迁移率。在原子尺度上，基于反应力场的分子动力学模拟将描述位错-位错和位错-孪晶相互作用的载流子浓度相关机制。在介观尺度上，光照度对应力-应变行为的影响将通过建立包含位错滑移和形变孪生的原子信息晶体塑性模型来量化。理论预测将通过机械测试和使用先进实验技术的材料表征来验证，这些技术包括纳米压痕、扫描探针显微镜、透射电子显微镜和电子背散射衍射。这项工作将为光伏半导体在光照下的变形机制提供新的物理图景，并全面了解一般光伏材料中的光机耦合效应。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Photovoltaic semiconductors are capable of converting light into electricity. They are the principal components of solar cells that provide renewable energy from sunlight. These semiconductors tend to fail in a brittle manner, limiting their general use to small-scale applications. New evidence shows though that the mechanical behavior of photovoltaic semiconductors is sensitive to sunlight, exhibiting the potential of relative malleability under illumination. The mechanisms underlying such light-mechanical coupling effect remains elusive. This award supports fundamental research to elucidate how light-induced excitation controls the mechanical behavior of photovoltaic semiconductors. The new knowledge is expected to offer strategies to design highly stable and durable photovoltaic devices, such as solar cells, transistors, light-emitting diodes, and photodetectors, providing the basis for extensive engineering applications. This award will also offer education and training for graduate and undergraduate students in interdisciplinary areas of mechanics, materials science and engineering, and photophysics. The award will promote diversity by involving women and underrepresented minorities in research activities.The photomechanical behavior of photovoltaic semiconductors is determined by light-induced deformation mechanisms such as dislocation and twinning. In this project, a multiscale modeling and experimental framework will be used to accurately characterize the influence of photoinduced electron-hole excitation on the dislocation and twining mechanics in cadmium telluride, a prototype photovoltaic semiconductor. On the sub-atomic scale, advanced quantum mechanics simulations will be performed to determine the influence of electron-hole pair on the energy and force barriers of dislocation and twin nucleation, as well as dislocation mobility. On the atomic scale, the carrier concentration dependent mechanisms of the dislocation-dislocation and dislocation-twin interactions will be characterized using reactive force field based molecular dynamics simulations. On the mesoscale, the light-illumination effect on the stress-strain behavior will be quantified by developing an atomically-informed crystal plasticity model that incorporates dislocation slip and deformation twinning. Theoretical predictions will be validated through mechanical testing and materials characterizations using advanced experimental techniques, including nanoindentation, scanning probe microscopy, transmission electron microscopy, and electron backscatter diffraction. This work will result in a new physical picture of the deformation mechanism of photovoltaic semiconductors under light illumination, and provide a comprehensive understanding of light-mechanical coupling effects in general photovoltaic materials.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.