OP: COLLABORATIVE RESEARCH: Integrated Simulation of Non-homogeneous Thin-film Photovoltaic Devices

OP：协作研究：非均质薄膜光伏器件的集成模拟

• 批准号: 1619904
• 负责人: Peter Monk
• 金额: $ 50万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2020-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1619904&HistoricalAwards=false
• 关键词: OP; COLLABORATIVE; RESEARCH; Integrated; Simulation

Solar cells are desirable as energy sources that neither use fossil fuels nor produce greenhouse gases. They must be designed to efficiently absorb sunlight and convert it to electricity. The solar cell needs to be sufficiently thick to absorb light across the solar spectrum. To reduce this thickness, and so reduce manufacturing cost, several layers of materials are used: first, to help light penetrate the solar cell, and then to trap it inside. Some of these layers are semiconductors in which electricity is generated, while others (for example, a periodically corrugated metallic back layer) may help absorption by trapping light near their surface. However, the amount of electricity generated by a solar cell does not just depend on absorption, but also on the transport of electrons within the layers of the solar cell. If the density of electrons decreases during transport, thereby trumping any gain in sunlight absorption, then a chosen light-management strategy will not be fruitful. The project team will develop an integrated pair of computer models that simultaneously predict the absorption of sunlight and the consequent electrical performance of the solar cell using modern techniques from numerical analysis. The codes will extend current simulation technology to allow for semiconductor layers with properties that vary from place to place and allow fully three-dimensional models of the device. Using their codes, the PIs will optimize device designs for best electricity generation. Definitive predictions will be provided about thin-film photovoltaic solar cells, thereby providing significant progress towards inexpensive and sustainable production of electricity. These codes will be made available to other photovoltaic researchers.The overall model of the thin-film photovoltaic solar cell will have a photonic submodel and an electrical submodel. In the photonic model, the quasi-periodic Maxwell's equations will be solved using edge finite elements. To improve flexibility, the PIs will analyze and implement a non-standard mortaring technique to take care of quasi-periodicity. Compatible electrical models will be analyzed and implemented using the Hybridizable Discontinuous Galerkin (HDG) method on hexahedral elements for the non-linear convection and diffusion problem governing drift and diffusion of electrical charge carriers. The HDG scheme will require a novel analysis to understand this non-linear convection-diffusion problem. Stability and convergence will be explored first for linear convection-diffusion problems, and the methodology will then be extended to an implicit-explicit time-stepping scheme for the drift-diffusion system. Besides a full 3D model, the PIs will develop a 2D model assuming translation invariance of the photovoltaic device in one transverse direction. The second step of the proposed research is to use the new simulation capability to design optimal nonhomogeneous thin-film photovoltaic solar cells via the Differential Evolution Algorithm. This will optimize for maximal photovoltaic electricity-generation efficiency. Additionally, domain and coefficient derivatives will be characterized and implemented to allow the computation of sensitivities and the use of gradient-based optimization. Detailed photonic-and-electrical modeling with doubly periodic back-reflectors and non-homogeneous light-absorbing layers will permit a major expansion of solar-cell design methodologies, besides yielding optimal designs for maximal photovoltaic electricity-generation efficiency.

太阳能电池作为既不使用化石燃料也不产生温室气体的能源是可取的。它们的设计必须能够有效地吸收阳光并将其转化为电能。太阳能电池需要足够厚，才能吸收太阳光谱中的光线。为了减少这种厚度，从而降低制造成本，使用了几层材料：首先，帮助光线穿透太阳能电池，然后将其困在里面。其中一些层是半导体，在其中发电，而另一些层(例如，周期性波纹金属背层)可能通过在其表面附近捕获光线来帮助吸收。然而，太阳能电池产生的电量不仅取决于吸收，还取决于太阳能电池各层内的电子传输。如果电子密度在传输过程中降低，从而超过了在吸收阳光方面的任何收益，那么选定的光管理策略将不会取得成果。该项目团队将开发一对综合的计算机模型，利用数值分析中的现代技术，同时预测太阳能电池的阳光吸收和相应的电气性能。这些代码将扩展当前的模拟技术，以允许特性因地而异的半导体层，并允许设备的完全三维模型。使用他们的代码，PI将优化设备设计，以实现最佳发电。将提供薄膜光伏太阳能电池的明确预测，从而在廉价和可持续的电力生产方面取得重大进展。这些代码将提供给其他光伏研究人员。薄膜光伏太阳能电池的整体模型将有一个光子子模型和一个电学子模型。在光子模型中，准周期麦克斯韦方程将用边有限元来求解。为了提高灵活性，采购经理将分析和实施一种非标准的迫击技术，以处理准周期性。对于电荷载流子漂移和扩散的非线性对流和扩散问题，将在六面体单元上使用杂交间断伽辽金(HDG)方法来分析和实现相容的电模型。HDG方案将需要一种新的分析来理解这个非线性对流扩散问题。首先讨论线性对流扩散问题的稳定性和收敛问题，然后将该方法推广到漂移扩散系统的隐式-显式时间推进格式。除了全3D模型外，PI还将开发一个2D模型，假设光伏设备在一个横向方向上的平移不变。研究的第二步是利用新的模拟能力通过差分进化算法来设计最优的非均匀薄膜光伏太阳能电池。这将优化最大的光伏发电效率。此外，还将表征和实施域和系数导数，以允许计算敏感度和使用基于梯度的优化。采用双周期后向反射器和非均匀光吸收层的详细的光电学建模将允许太阳能电池设计方法的重大扩展，并产生最大光伏发电效率的优化设计。