Events

Computational and Experimental Screening of Mixed-Metal Perovskite Compositions*

October 27, 2015 at 12 noon/36-462

Matthew Klug
MIT/Department of Biological Engineering

Although solar cells with impressive power conversion efficiencies have been demonstrated using lead-based metal halide perovskites, there are concerns regarding the inherent toxicity and long-term stability of these materials. This talk will focus on recent computational and experimental efforts that explore the feasibility of simultaneously addressing both of these issues by fabricating active layers with mixed-metal compositions, where a portion of the metal content in the perovskite film has been replaced with an alternative, less-toxic metal species. Relevant electronic properties such as the material band gap, carrier effective masses, and band edge locations were theoretically evaluated using density functional theory (DFT). By computationally screening through a series of mixed-metal compositions that spans the periodic table, several promising candidates were identified that preserve the excellent electronic properties of the methylammonium lead triiodide perovskite, MAPbI3, while simultaneously reducing material toxicity. The computational effort was paired with an exhaustive experimental screening study that systematically evaluated how replacing various amounts of lead with nine different metal species impacts material and electronic properties as well as device performance. These findings reveal that introducing a second metal species can influence film morphology, modify the material band gap, shift the band edge locations, impact photoluminescence, and improve photovoltaic performance. The aggregate data provides enough information for us to propose feasible physical mechanisms that explain trends in performance and are consistent with both empirical observations and computations. Furthermore, this work will present preliminary results that suggest some mixed-metal compositions also demonstrate superior resistance to degradation at elevated temperatures. While further experimentation is required to evaluate whether mixed-metal compositions would improve performance of solar cells utilizing different device architectures or perovskite synthesis techniques, this study presents encouraging evidence that introducing alternative metal species can have beneficial impacts on device performance and stability, while simultaneously mitigating toxicity.

Matt Klug is a post-doctoral researcher in Prof. Angela Belcher’s Biomolecular Materials Group at MIT, where he studies emerging solution-processed solar cells and synthesizes photoactive nanocomposites using biological materials.

*This talk is part of the Perovskites Seminar Series organized by Sam Stranks and sponsored by the Center for Excitonics. For more info contact Sam Stranks: stranks@mit.edu