Bifacial all perovskite tandem solar cells for a sustainable energy future

太阳能是一种清洁、可再生和最丰富的能源，但来自太阳能电池的电能仍然只占全球发电量的很小一部分。实现高效和低成本的光伏组件对于使太阳能成为可持续能源未来真正可行和有吸引力的解决方案至关重要。串联太阳能电池具有比单结器件高得多的热力学效率上限。由于这两种子电池的低成本溶液处理，全钙钛矿串联太阳能电池具有巨大的潜力，可以将能量的平准化成本降低到硅基单结和多结电池的水平。在过去的五年中，全钙钛矿叠层太阳能电池的效率从10.8%提高到25%以上，但它们尚未充分发挥这项技术的潜力。该项目旨在通过双面串联结构将全钙钛矿串联电池的等效效率提高到33%以上，并解决相关的基本材料和器件挑战。该项目的成功可以产生一种有前途的可再生能源，其成本与化石能源相比具有竞争力，从而减少温室气体排放和环境污染。该项目将通过跨学科研究为研究生和本科生提供培训，并将为他们带来企业家思维。该项目的一个主要重点是增加少数群体的参与，并通过在查佩尔山的北卡罗来纳州大学开展的几项外联活动，使广大受众尽早了解研究成果。全钙钛矿叠层太阳能电池的效率主要受到宽带隙钙钛矿电池的大于通常的开路电压赤字和窄带隙钙钛矿电池的低外部量子效率的限制。我们建议开发双面全钙钛矿叠层电池，在含锡窄带隙钙钛矿电池上无损伤地沉积透明电极，其效率上限超过33%。双面串联结构不仅提高了实际功率转换效率的上限，而且将宽带隙电池的最佳带隙移到较低值，从而避免了较大带隙钙钛矿电池的大开路电压赤字问题。此外，我们将提高窄带隙钙钛矿电池的光捕获效率。为了克服窄带隙钙钛矿电池的低外部量子效率问题，该项目将探索限制含锡窄带隙钙钛矿的载流子扩散长度的基本过程，并使用专门的添加剂解决相关缺陷。此外，该项目还将全面了解地面反射的反射波效应、天气条件和模块安装条件对双面全钙钛矿叠层电池效率的影响，从而为改进太阳能电池设计提供有价值的反馈。这项研究将解决双面全钙钛矿叠层太阳能电池的基本理解，并提供一个有前途的可再生能源与低平准化能源成本。该奖项反映了NSF的法定使命，并已被认为是值得支持的评估使用基金会的智力价值和更广泛的影响审查标准。

Solar energy is a clean, renewable and most abundant energy resource, however electric energy from solar cells still only contributes to a very small portion of the global electricity generation. Achieving highly efficient and low-cost photovoltaic modules is critical to make solar energy a truly viable and attractive solution for a sustainable energy future. Tandem solar cells have a much higher thermodynamic efficiency upper limit than single junction devices. Due to low-cost solution processing for both subcells, the all-perovskite tandem solar cells have enormous potential to reduce the levelized cost of energy below those of silicon based single-junction and multijunction cells. Tremendous progress has been made over the past five years to improve the efficiency of all-perovskite tandem solar cells from 10.8% to over 25%, but they have not yet reached the full potential of this technology. This project aims at increasing the equivalent efficiency of all-perovskite tandem cells to over 33% via a bifacial tandem architecture and address the related fundamental material and device challenges. The success of this project can yield a promising renewable energy source with cost competitiveness to fossil energy, thus reducing greenhouse gas emissions and environmental pollution. The project will provide training to graduate and undergraduate students through interdisciplinary research and will bring them an entrepreneur mindset. A strong focus of the project is on increasing participation of minorities and providing early exposure of research to a broad audience through several outreach activities at The University of North Carolina at Chapel Hill. The efficiency of all-perovskite tandem solar cells is primarily limited by the larger than usual open circuit voltage deficit of wide-bandgap perovskite cells and the low external-quantum-efficiency of narrow-bandgap perovskite cells. We propose to develop bifacial all-perovskite tandem cells with a damage-free deposition of transparent electrodes on tin-containing narrow-bandgap perovskite cells which have a much higher efficiency upper limit of over 33%. The bifacial tandem architecture not only enhances the upper limit of realistic power conversion efficiency, but also shifts the optimal bandgap of wide-bandgap cell to a lower value, thus avoids the large open circuit voltage deficit problem for larger bandgap perovskite cells. In addition, we will enhance light harvesting efficiency of the narrow-bandgap perovskite cells. In order to overcome the low external-quantum-efficiency issue in the narrow bandgap perovskite cells, this project will explore the fundamental processes that limit the carrier diffusion length of tin-containing narrow bandgap perovskites and address the related defects with specialized additives. Moreover, this project will provide a comprehensive understanding of the impact of ground reflected albedo effects, weather conditions, and module installation conditions on the efficiency of bifacial all-perovskite tandem cells, in turn, providing valuable feedback to improve solar cell design. This research will address the fundamental understanding of bifacial all-perovskite tandem solar cells and provide a promising renewable energy with low levelized cost of energy.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.