Collaborative Research: Photomechanical Behavior in Photovoltaic Semiconductors

光伏半导体能够将光转化为电。它们是太阳能电池的主要组成部分，可以从阳光中提供可再生能源。这些半导体往往以一种脆弱的方式失效，限制了它们在小规模应用中的普遍使用。新的证据表明，光伏半导体的力学行为对阳光很敏感，在光照下表现出相对延展性的潜力。这种光-机械耦合效应的机制尚不清楚。该奖项支持阐明光诱导激发如何控制光伏半导体机械行为的基础研究。这些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、材料科学与工程和光物理等跨学科领域的研究生和本科生提供教育和培训。该奖项将通过让妇女和未被充分代表的少数民族参与研究活动来促进多样性。光电半导体的光电力学行为是由光致变形机制，如位错和孪晶决定的。在本项目中，将使用多尺度建模和实验框架来准确表征光诱导电子空穴激发对光电半导体原型碲化镉中位错和缠绕力学的影响。在亚原子尺度上，将进行先进的量子力学模拟，以确定电子-空穴对位错和孪核的能垒和力垒以及位错迁移率的影响。在原子尺度上，将利用基于反应力场的分子动力学模拟来表征位错-位错和位错-孪晶相互作用的载流子浓度依赖机制。在中尺度上，光照对应力-应变行为的影响将通过开发包含位错滑移和变形孪晶的原子信息晶体塑性模型来量化。理论预测将通过使用先进的实验技术，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，进行机械测试和材料表征来验证。这项工作将为光照射下光伏半导体的变形机制提供一个新的物理图景，并对一般光伏材料的光-机械耦合效应提供一个全面的认识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.