SOLAR Collaborative: Multiplasmonic Light Harvesting for Thin Film Solar Cells

该项目由材料研究部、化学部和数学科学部共同资助。技术：一个由宾夕法尼亚州立大学的化学家、材料科学家和工程师组成的团队，与特拉华大学的一位数学家一起研究太阳能电池的光捕获薄膜，该薄膜包含等离子体纳米结构与周期性介电体耦合。该项目将亚波长金属结构的强光散射概念与光子晶体的捕光和导光特性联系起来。这些结构被称为多等离子体，因为它们支持多个表面等离子体偏振子（SPP）模式的传播，并且可以利用s偏振和p偏振入射光。它们为大幅提高薄膜光伏电池的光利用率提供了希望。这一概念在薄膜半导体和平面介电光聚光结构中进行了计算和实验研究。采用严格耦合波法模拟和优化光的散射和传播。由于这些计算是耗时的，因此计划进行数学研究以开发更有效的算法，这些算法将包含提供物理上有意义的解决方案所需的光学特性。然后将开发一个全三维时域仿真工具，以实现多等离子体结构的宽带建模。与计算工作相一致，多等离子体概念在几个实验架构中进行了测试和验证。其中最简单的是一个传统的SPP散射层，它由一个金属背衬膜和散射中心网格组成，在一个包含多晶或非晶半导体层的薄膜多结电池上。这种结构允许计算模型在光伏电池中进行验证，并有望量化极化和多模式效应。采用异质集成硅微电池，研究了含周期性氧化物或聚合物介电层的平面聚光器结构作为光伏组件。这些设计扩展到结合染料敏化太阳能电池和多等离子体硅电池的光谱分裂模块。为了制造这些模块，人们开发了新的光学纳米结构和新的图像化技术。非技术：太阳能光伏发电是一种可再生资源，有可能对全球能源经济产生巨大影响，大规模实施受到成本的限制。这个项目的目标是探索太阳能电池捕光的新原理。这种方法可以使太阳能电池的硅含量比传统电池少五倍，同时提供相同的功率。这个概念是结合两种光学纳米结构：(1)非常小的金属颗粒，众所周知，它们会强烈散射光线；(2)有图案的绝缘体，可以衍射光线——这与蛋白石和蝴蝶翅膀的颜色产生的现象相同。理论预测和初步实验证实，这些组合结构的薄膜具有特别好的光捕获能力。挑战在于研究不同组合的特性，为此必须开发更有效的数学工具和制造方法，并证明它们可以以可制造的方式集成到太阳能电池中。该项目具有多学科性质，吸引研究生参与纳米材料合成和图像化、太阳能电池模块设计、光学和电气测量、建模和数学算法开发等主题的研究。宾夕法尼亚州立大学和特拉华州的本科生也参与了这个项目。

This project is co-funded by the Divisions of Materials Research, Chemistry, and Mathematical Sciences.Technical: A team of chemists, materials scientists, and engineers at Pennsylvania State University is joined by a mathematician at the University of Delaware to investigate light-harvesting thin films for solar cells that contain plasmonic nanostructures coupled to periodic dielectrics. The project links the concepts of strong light scattering by sub-wavelength metallic structures with the light-trapping and light-guiding properties of photonic crystals. These structures are called multiplasmonic because they support the propagation of multiple surface plasmon-polariton (SPP) modes and can utilize both s- and p-polarized incident light. They offer promise for substantially increasing the utilization of light in thin film photovoltaic cells. This concept is explored computationally and experimentally in thin film semiconductor and planar dielectric light-concentrating architectures. The Rigorous Coupled Wave Approach is used to simulate and optimize light scattering and propagation. Because these calculations are time-intensive, mathematical research is planned to develop more efficient algorithms that will incorporate the optical properties needed to provide physically meaningful solutions. A fully 3-D time domain simulation tool will then be developed to enable broadband modeling of the multiplasmonic structures. In concert with the computational effort, the multiplasmonic concept is tested and validated in several experimental architectures. The simplest of these is a conventional SPP scattering layer, consisting of a metal backing film with a grid of scattering centers on a thin film multi-junction cell containing layers of polycrystalline or amorphous semiconductors. This structure allows the computational model to be validated in a photovoltaic cell and is expected to quantify polarization and multi-mode effects. Planar concentrator architectures containing periodic oxide or polymer dielectric layers with heterogeneously integrated silicon microcells are studied as photovoltaic modules. These designs are extended to a spectrum-splitting module that combines dye-sensitized solar cells and multiplasmonic silicon cells. New optical nanostructures and new patterning techniques are developed in order to fabricate these modules.Non-technical: The large-scale implementation of solar photovoltaic power, a renewable resource that has the potential to dramatically impact the global energy economy, is limited by cost. The goal of this project is to explore a new principle for light trapping in solar cells. This approach could enable the design of solar cells that contain five times less silicon than conventional cells, while delivering the same amount of power. The concept is to couple two kinds of optical nanostructures: (1) very small metal particles, which are well known to scatter light strongly, and (2) patterned insulators that diffract light - the same phenomenon that gives rise to the colors of opals and butterfly wings. Theory predicts and preliminary experiments confirm that thin films of these combined structures are particularly good at light trapping. The challenge is to investigate the properties of different combinations, for which more efficient mathematical tools as well as fabrication methods must be developed, and to demonstrate that they can be integrated into solar cells in a manufacturable way. This project, with its multidisciplinary nature, engage graduate students in research that bridges topics in nanomaterials synthesis and patterning, solar cell module design, optical and electrical measurements, modeling, and mathematical algorithm development. Undergraduate honors students are also involved in this project at both Penn State and Delaware.