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

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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.