EAGER: TDM Solar Cells: Collaborative Research: Exploration of High Open-Circuit Voltage and Stable Wide-Bandgap Cu2BaSnS4 Solar Cells for Monolithic Tandem Cell Applications

低成本和高转换效率太阳能电池的成功开发将使太阳能电力作为美国可持续能源经济的丰富电力来源得到广泛使用。生产最高效太阳能电池的成熟方法是将两种材料串联堆叠，使得一种材料吸收太阳光谱的蓝色部分，而另一种材料吸收红色部分。然而，到目前为止，大多数成功应用这项技术的太阳能电池只能使用高度专业化的单晶材料来生产。生长方法的复杂性以及昂贵的单晶衬底的使用阻碍了这些串联太阳能电池实现低成本。该项目建议探索稳定和低成本的多晶薄膜半导体，特别是一种吸收太阳光谱蓝色部分的半导体，以实现低成本和高转换效率的串联太阳能电池。研究和教育的一体化将培养和指导研究生和本科生的跨学科技能，这些技能对于他们进入工作场所开发创新解决方案至关重要，并有助于美国在新兴电子领域的领导地位。拟议的项目将有利于研究生和本科生的教育和研究，并为他们成为未来能源行业的劳动力做好准备。技术该项目将发展基础科学知识，从而制造稳定高效的宽带隙太阳能电池，并最终用两种不同的材料制造串联电池。多晶薄膜光伏器件具有比外延薄膜低得多的生产成本和复杂性，但它们的最终转换效率不能超过单结太阳能电池的理论Shockley-Queisser极限。由两种不同材料制成的串联电池，都是低成本的多晶薄膜，将是下一代低成本和超高转换效率光伏器件的理想选择。未能实现高转换效率的多晶薄膜串联器件的主要原因是缺乏使用合适的多晶宽带隙半导体材料的高效上单元。由于串联器件的效率主要取决于两种半导体的开路电压组合，因此一个有前途的顶层电池必须能够产生高开路电压。该项目将取得几项突破性成果：1)将开发出合成高质量宽带隙薄膜的方法；2)将彻底了解这种宽禁带半导体的基本缺陷物理；3)将发现并优化形成前后结的缓冲层；4)将展示具有高转换效率和高开路电压的宽带隙顶电池；5)如果成功，将能够制造出低成本和高转换效率的薄膜串联太阳能电池。

AbstractNontechnicalThe successful development of low-cost and high conversion efficiency solar cells will enable widespread use of solar electricity as an abundant source of electricity for a sustainable energy economy in the U.S. A proven method for producing the most efficient solar cells is to stack two materials in tandem such that one material absorbs the blue part of the solar spectrum and the other the red part. However, most solar cells that successfully employ this technique to date can only be produced using highly specialized single crystal materials. The complexity of growth methods and their use of expensive single crystal substrates have prevented these tandem solar cells from achieving low cost. This project proposes to explore stable and low-cost polycrystalline thin-film semiconductors, in particular one that absorbs the blue part of the solar spectrum, to enable low-cost and high conversion efficiency tandem solar cells. The integrative nature of the research and education will train and mentor graduate and undergraduate students in cross-disciplinary skills that are essential for developing innovative solutions as they enter the workplace and contribute to the U.S. leadership in the burgeoning field of electronics. The proposed project will benefit the education and research of graduate and undergraduate students and prepare them as the workforce of future energy industries.TechnicalThis project will develop the fundamental scientific knowledge that will lead to the fabrication of stable and efficient wide bandgap solar cells and eventually tandem cells made with two dissimilar materials. Polycrystalline thin film photovoltaic devices offer much lower production cost and complexity than epitaxial thin films, but their ultimate conversion efficiencies cannot go beyond the theoretical Shockley-Queisser limit for single-junction solar cells. A tandem cell made with two dissimilar materials, both low-cost polycrystalline thin films, would be an ideal choice for next generation low-cost and ultra-high conversion efficiency photovoltaic devices. The chief reason for failure to achieve high conversion efficiency polycrystalline thin-film tandem devices is the lack of an efficient top cell using suitable polycrystalline wide-bandgap semiconductor materials. Since the efficiency of a tandem device predominantly depends on the combined open circuit voltages of both semiconductors, a promising top cell must be able to produce high open circuit voltage. The proposed project will yield several break-through results: 1) approaches for synthesizing high-quality wide bandgap thin films will be developed; 2) fundamental defects physics of such wide bandgap semiconductors will be thoroughly understood; 3) buffer layers forming front and back junctions will be discovered and optimized; 4) Wide-bandgap top cells with high conversion efficiency and high open circuit voltage will be demonstrated; 5) If successful, it will enable the fabrication of low-cost and high conversion efficiency thin-film tandem solar cells.