SEP: Earth-abundant thin-film solar cells as a sustainable solar energy pathway

NSF可持续能源路径(SEP)计划在NSF可持续发展科学、工程和教育(SEES)倡议的框架下，将支持严法教授和托莱多大学同事的研究计划。这支高度多学科的研究团队由物理、材料科学、工程、化学、社会经济学、环境科学和教育等领域的专家组成。该项目的目标是开发必要的概念、材料和工艺，以经济地从地球上丰富的、环境友好的(EAEB)材料生产环境友好型薄膜太阳能电池，包括FeS2、Cu2S、CuO、Zn3P2和Cu2ZnSnS4(CZTS)。为了实现高效的EAEB太阳能电池，研究团队提出了两个新概念：(1)用于低载流子迁移率和低结构稳定性的EAEB无机材料的体同质结(例如，FeS2、Cu2S和CuO)和(2)用于Zn3P2和CZTS基薄膜太阳能电池的异质同质双结(HHDJ)。块状同质结的概念将通过组装纳米晶体(NC)来实现，这些纳米晶体的表面将经过精心设计，以包含富阳离子的区域。组装完成后，NCS将形成一个由电子和空穴通道组成的三维互连网络，由于同质结拓扑结构，该网络可以促进电荷分离和转移，并最大限度地降低复合效率。HHDJ将通过使用具有现场监测的专用物理气相沉积系统精确控制结化学来实现，包括实时电子碰撞发射光谱和实时光谱椭偏测量。HHDJ的概念结合了异质结和同质结的优点：同质结最大限度地减少了抢效率的复合，而异质结增强了电荷分离和转移，从而实现了最佳的太阳能电池性能。研究团队将通过生命周期工具同时开发和分析我们新的太阳能电池系统和制造工艺的可持续性，其中将同时开发生命周期成本计算(LCC)、环境生命周期评估(LCA)和社会生命周期评估(SLCA)，以创建全面的生命周期可持续评估(LCSA)。为了实施可持续发展战略，将采用一种新的动态方法，对不同的情景进行迭代建模，以确定参数的具体相互作用，并最终确定最可持续的情景。为了解决教育/劳动力发展问题，研究小组将针对各级学生的关键教育目标。研究团队还将采用一种综合方法，来自广泛不同背景和专业领域的学生将共同努力解决复杂的现实世界问题。这种方法将进一步加强协同效应，拓宽教育目标，并建立真正的团队理念。该项目将产生至少两个科学影响：(1)彻底了解对于使用无毒和富含地球的材料实现可持续太阳能途径至关重要的基础科学和工程问题，以及(2)设计经济、环境和社会可持续的可再生能源，特别是太阳能发电途径的新科学和教育范式。通过在开发材料和工程技术方面直接结合社会和行业的需求，该项目应成为可再生能源新技术可持续发展的变革性模式。

The NSF Sustainable Energy pathways (SEP) Program, under the umbrella of the NSF Science, Engineering and Education for Sustainability (SEES) initiative, will support the research program of Prof. Yanfa Yan and co-workers at the University of Toledo. The highly multi-disciplinary research team consists of experts in physics, materials science, engineering, chemistry, socioeconomics, environmental science, and education. The objective of the project is to develop the concepts, materials, and processes necessary to economically produce environmentally friendly thin-film solar cells from earth-abundant, environmentally benign (EAEB) materials including FeS2, Cu2S, CuO, Zn3P2 and Cu2ZnSnS4 (CZTS). To achieve high efficiency EAEB solar cells, the research team proposes two new concepts: (1) a bulk homojunction for EAEB inorganic materials that have low carrier mobility and low structural stability (e.g., for FeS2, Cu2S, and CuO) and (2) a hetero-homo dual-junction (HHDJ) for Zn3P2- and CZTS-based thin-film solar cells. The bulk homojunction concept will be realized by assembling nanocrystals (NCs) with surfaces that will be carefully engineered to contain cation-rich domains. Upon assembly, the NCs will form a three-dimensional interconnected network of electron and hole channels that can facilitate charge separation and transfer with minimal efficiency-robbing recombination due to the homojunction topology. The HHDJ will be achieved by accurate control of the junction chemistry using dedicated physical vapor deposition systems with in situ monitoring, including real-time electron impact emission spectroscopy and real-time spectroscopic ellipsometry. The HHDJ concept combines the benefits of the heterojunction and the homojunction: the homojunction minimizes efficiency-robbing recombination while the heterojunction enhances the charge separation and transfer, leading to optimal solar cell performance. The research team will concomitantly develop and analyze the sustainability of our new solar cell systems and manufacturing processes through life cycle tools where life cycle costing (LCC), environmental life cycle assessment (LCA), and social life cycle assessment (SLCA) will be developed simultaneously to create a comprehensive life cycle sustainability assessment (LCSA). To implement LCSA, a new dynamic approach will be used whereby different scenarios will be iteratively modeled to identify the specific interactions of the parameters and, ultimately, the most sustainable scenarios. To address education/workforce development, the research team will target critical educational goals for students at all levels. The research team will also employ an integrative approach wherein students from widely varying backgrounds and fields of expertise will work together to solve complex real world problems. This approach will further reinforce synergy, broaden educational goals, and build a true team philosophy. This project will yield at least two scientific impacts: (1) a thorough understanding of the fundamental science and engineering issues that are critical for realizing a sustainable solar energy pathway using non-toxic and earth-abundant materials, and (2) new science and education paradigms for designing economically, environmentally, and socially sustainable renewable energy and, specifically, solar electricity pathways. By directly integrating the needs of society and industry in developing the materials and engineering technology, this project should serve as a transformational model for the sustainable development of new renewable energy technologies.