NSF Award
2404765
Photovoltaic technology, as a sustainable and environmentally friendly energy source, is poised to meet our ever-expanding energy demands and contributing to the global carbon-neutral goal. Notably, perovskite solar cells (PSCs) have seen a surge in the sunlight-to-electricity conversion efficiency from 3.8% to 26.1%. However, the most efficient PSCs rely on lead-based perovskite (PbPVK), raising concerns about its toxicity to both human health and aquatic ecosystems. Tin-based perovskite (SnPVK) is regarded as a promising alternative for its low toxicity, high carrier mobility, and strong light absorption coefficient. Despite progress having been made, the efficiency and stability of tin perovskite solar cells (SnPSCs) are still inferior to their lead counterparts. The challenges with SnPSCs are primarily due to defects at the interfaces of SnPVK and charge transport layers and relative thin SnPVK films, which diminishes the sunlight-to-electricity conversion efficiency and reduces the lifetime of SnPSCs. Here, we propose a synergistic approach to tackle these challenges by minimizing the voltage loss and maximizing the current to enhance performance and stability of SnPSCs. The successful completion of this project will advance the knowledge of semiconductors and device physics of thin film solar cells, which could lead to the transformation of clean energy techniques. This highly interdisciplinary research project will provide outstanding training opportunities for graduate and undergraduate students from underrepresented groups. The knowledge gained from this project will be disseminated through the local outreach activities such as the “Wondering the Light” workshop for Expanding Your Horizons, designed to inspire middle school girls to engage with STEM. <br/><br/>The primary objective of this project is to conduct fundamental research through a synergetic approach including molecular structure design, crystallization kinetics studies, electronic structure tuning, electromagnetic simulations, and nanofabrication of resonant nanostructures to achieve highly efficient and stable SnPSCs. The research team aims to improve the efficiency of SnPSCs by both minimizing the loss of open-circuit voltage VOC and maximizing the gain of short-circuit current density JSC via 1) novel self-assembled monolayer (SAM) as the bottom contact for p-i-n SnPSCs to reduce the defect density at the bottom buried interface; 2) rationally designed passivation molecules as top surface termination to promote favorable band bending at the electron transport layer and SnPVK interface; and 3) in-situ formed resonant nanostructures atop SnPVK films to enhance the light harvesting at the band edge, near infrared region. The intellectual merit is driven by the hypotheses: 1) the VOC of SnPSCs could be enhanced via using novel SAM to guide the formation of a thin 2D SnPVK layer at the buried SnPVK interface to reduce the defect density at the SAM/SnPVK interface and using non-invasive ligands that mitigate 2D-perovskite formation to passivate top surface defects, suppress Sn-vacancies, favor band alignment with ETL, and enhance electron transport; and 2) the JSC of SnPSCs could be enlarged via implementing resonant nanostructures in the form of gratings on the SnPVK film surface to increase photon harvesting in the long wavelength. This project will provide new insights into the fundamental physical and chemical interactions between SnPVK with SAM molecules and passivation molecules, the fundamental electronic structure changes after passivation molecules reacted with the grain boundary of SnPVK, and the photophysical property of supercell resonant nanostructures. By fundamentally understanding the structural and optoelectronic properties of SnPVK with modified bottom and top interfaces and the effect of resonant nanostructures on light harvesting, the general principles to guide the development of highly efficient, stable tin perovskite solar cells will be elucidated.<br/><br/>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.
