Excellence in Research: Spontaneous Nucleation Strategy for High-Quality Perovskite Films

太阳能被认为是解决能源危机问题最有前途的可再生能源之一，因为它清洁、免费、无碳排放。太阳能电池可以将太阳光直接转化为电能，利用光伏效应为电子设备供电。目前，以硅太阳能电池为代表的先进太阳能转换技术还不能满足低成本、高能量转换效率的要求，不能广泛应用。另外，钙钛矿太阳能电池（PSCs）代表了一系列有前途的光伏系统，具有低成本和高能量转换效率。自2009年以来，psc已经实现了25.7%的认证功率转换效率。钙钛矿薄膜主要采用抗溶剂辅助法制备。抗溶剂辅助法在重现性高、生产规模大、装置尺寸大等方面不适合实际应用。这个卓越研究（EiR）项目致力于利用挥发性溶剂通过非抗溶剂方法制备高效钙钛矿太阳能电池。所提出的研究方法在制备高质量钙钛矿薄膜方面显示出巨大的潜力，因为薄膜的生长是由溶剂挥发通过自发和同时过饱和成核策略引起的。本项目将对通过挥发性溶剂和添加剂制备和调节钙钛矿前驱体，通过非抗溶剂方法控制高质量钙钛矿膜的生长提供批判性的理解。本项目还将研究非抗溶剂方法中溶剂-溶质化学与PSC器件性能之间的关系。该EiR项目基于非抗溶剂方法和先进的表征技术的可调节钙钛矿薄膜生长，将为在挥发性溶剂存在下晶体生长的溶质-溶剂化学提供见解，并通过非抗溶剂方法开发钙钛矿薄膜生长原理。所提出的研究将提供薄膜生长和细胞性能之间的桥梁，包括化学键、配位、成核和生长以及细胞性能。本项目将1)探索前驱体制备过程中碘铅酸盐的演化过程和溶剂挥发过程中钙钛矿晶体成核过程，研究溶液中碘铅酸盐与溶剂、添加剂之间的关系。2)研究薄膜的生长情况，包括薄膜覆盖、厚度、缺陷、裂纹和针孔，以及溶剂挥发、前驱体老化和碘铅配合物对薄膜生长的影响。3)研究湿膜到固体钙钛矿膜的相变及钙钛矿膜的光伏性能。4)优化取向钙钛矿晶体生长，朝着高质量、少缺陷、大晶粒、大面积、高再现性薄膜的方向发展。该项目将导致通过溶质-溶剂相互作用的非抗溶剂方法制备钙钛矿薄膜的革命。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。

NON-TECHNICAL SUMMARYSolar energy is believed to be one of the most promising renewable energies to solve the energy crisis problem because it is clean, free, and has no carbon emissions. Solar cells can convert sunlight directly to electricity to power electronic devices by the photovoltaic effect. Currently, state-of-the-art solar energy conversion technologies, for example, silicon solar cells cannot meet the requirements of low cost and high energy conversion efficiency to enable broad use. Alternatively, perovskite solar cells (PSCs) represent a family of promising photovoltaic systems for low-cost and high energy conversion efficiency. To date, PSCs have achieved a certified power conversion efficiency of 25.7% since 2009. The perovskite films are predominantly prepared by the antisolvent-assisted method. The antisolvent-assisted method is not suitable for practical applications in terms of high reproducibility, large-scale production, and large-size devices. This Excellence in Research (EiR) project addresses the use of volatile solvents to prepare high-efficiency perovskite solar cells by a non-antisolvent method. The proposed research method exhibits significant potential in the fabrication of high-quality perovskite films because the film growth is caused by solvent volatilization via a spontaneously and simultaneously supersaturated nucleation strategy. This project will provide a critical understanding of the perovskite precursor prepared and adjusted by volatile solvents and additives to control the high-quality perovskite film growth via a non-antisolvent method. This project will also study the relationship between solvent-solute chemistry and PSC device performance in the non-antisolvent method. TECHNICAL SUMMARYThis EiR project, based on adjustable perovskite film growth by non-antisolvent methods and advanced characterization techniques, will provide insights into tailoring the solute-solvent chemistry in crystal growth in the presence of volatile solvents and develop perovskite film growth principles by non-antisolvent methods. The proposed investigations will provide the bridge between film growth and cell performance comprehensively including chemistry bonding, coordination, nucleation and growth, and cell performance. This project will 1) Probe the iodoplumbates evolution during the precursor preparation and perovskite crystal nucleation process during the solvent volatilization and investigate the relationship between iodoplumbates, solvents, and additives in the solution. 2) Investigate film growth in terms of film coverage, thickness, defects, cracks, and pinholes as a function of solvent volatilization, precursor aging, and iodoplumbate coordination complexes. 3) Study the phase transition from wet films to solid perovskite films and the photovoltaic properties of the perovskite films. 4) Optimize the oriented perovskite crystal growth toward high quality, few defects, large grains, large area, and high reproducibility films. This project will lead to a revolution of perovskite film fabrication by non-antisolvent methods via solute-solvent interactions.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.