This CAREER project aims to develop high efficiency Pb-free perovskite solar cells and determine the stability of these novel materials. Pb-based organic-inorganic halide perovskite (OIHP) solar cells have shown tremendous promise with big leap in efficiency in less than a decade. However, due to presence of Pb and poor stability, these materials may pose issues for widespread use and commercialization of OIHP solar cells. The research community has not yet come up with a high performance alternative to Pb-based OIHP solar cells, primarily due to material defects. This project will develop air-stable and low defect density Pt-Ni and Sn-Ge based perovskite solar cells. Success in this project will result in development of a model system for Pb-free perovskite solar cells with stable buffer and contact materials. Lifetime prediction and levelized cost of energy (LCOE) models will be developed to determine the effect of Pb replacement on cell cost, energy yield, efficiency, degradation rates, encapsulation costs and recycling. In addition to these scientific advancements, PI will train underrepresented minority graduate and undergraduate students on materials for energy applications. This CAREER project will also train the next generation workforce for solar energy jobs in Nevada at community colleges and UNLV. Dedicated workshop series to identify the fundamental roadblocks for development of high efficiency and Pb-free perovskite materials will be hosted in collaboration with academia and industry partners.

Organic-inorganic halide perovskites (OIHPs) have shown significant progress as low-cost, solution printable semiconductors with superior optoelectronic properties. For photovoltaic applications, these materials have achieved remarkable power conversion efficiency of 25.2% single-junction and 29.1% perovskite-Si tandem devices. Despite the exceptional performance of OIHPs, toxicity of Pb, thermal stability, and stability due to ion migration are fundamental materials issues that need to be solved. The superior optoelectronic properties of Pb-based OIHPs have not yet been reproduced in Pb-free compositions due to high defect density and low absorption coefficient. The objectives of the proposed research are to develop all inorganic mixed halide-chalcogenide Pb-free perovskite photoabsorbers ABX3 and A2BX6 (A = Cs; B = Ge/Sn, Pt/Ni; X = I, Cl, Br, O, S) with tunable bandgap and high carrier lifetime. Dopant-free inorganic electron and hole transport layers with optimal band offsets will be developed for high efficiency and stable planar solar cells. Proposed work will address following: (1) solution processing of stable mixed halide-chalcogenide Pb-free perovskite thin films with low midgap defect density and high absorption coefficient; (2) stability and degradation mechanisms under junction bias, light illumination, heat, oxygen, UV and humidity; (3) surface and interface defect passivation with improved electron and hole transport layers; (4) high efficiency and stable Pb-free perovskite solar cells; (5) Accelerated stress testing protocols and numerical models for lifetime prediction and LCOE for Pb-free perovskite solar cells; and (6) cost-stability-performance trade-off analysis of Pb vs. Pb-free perovskite solar cells. Achieving a fundamental understanding of how to control the electronic, chemical, electrochemical, and dynamics behavior of Pb-free perovskite photoabsorbers will enable an entirely new generation of wide bandgap semiconductors for PV applications and beyond. Key international collaborations will be formed to address critical challenges for high efficiency Pb-free perovskite solar cells. This project is jointly funded by the division of Electrical, Communications and Cyber Systems (ECCS) and the Established Program to Stimulate Competitive Research (EPSCoR).

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.

National Science Foundation (NSF)
Division of Electrical, Communications and Cyber Systems (ECCS)
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Rosa Alejandra Lukaszew
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University of Nevada Las Vegas
Las Vegas
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