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，但太阳能电池产生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是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的关键。串联太阳能电池具有比单结装置高得多的热力学效率上限。由于两种亚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低于硅基单结和多结电池的水平。在过去的五年里，全钙钛矿串联太阳能电池的效率从10.8%提高到25%以上，取得了巨大的进步，但他们还没有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，并解决相关的基础材料和设备挑战。该项目的成功将产生一种具有成本竞争力的可再生能源，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，并培养他们的企业家思维。该项目的一个重点是增加少数民族的参与，并通过北卡罗来纳大学教堂山分校的几项外展活动，使研究尽早接触到广泛的受众。全钙钛矿串联太阳能电池的效率主要受到宽禁带钙钛矿电池开路电压亏大和窄禁带钙钛矿电池外量子效率低的限制。我们提出在含锡窄带隙钙钛矿电池上无损伤沉积透明电极的双面全钙钛矿串联电池，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，而且将宽禁带电池的最佳带隙移至较低的值，从而避免了大带隙钙钛矿电池的大开路电压亏缺问题。此外，我们将提高窄带隙钙钛矿电池的光收集效率。为了克服窄带隙钙钛矿电池外量子效率低的问题，本项目将探索限制含锡窄带隙钙钛矿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，该项目将全面了解地面反射反照率效应、天气条件和组件安装条件对双面全钙钛矿串联电池效率的影响，进而为改进太阳能电池设计提供有价值的反馈。本研究将解决对双面全钙钛矿串联太阳能电池的基本认识，并提供一种具有低水平成本的有前途的可再生能源。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.