Collaborative Research: Design and Discovery of Entropy-Stabilized Perovskite Halides for Optoelectronics

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PART 1: NON-TECHNICAL SUMMARYPerovskite halides are an exciting family of materials that can be prepared by low-temperature synthesis methods and are promising for a wide variety of optoelectronic applications. With this project, which is jointly funded by the Solid State and Materials Chemistry program in the Division of Materials Research and the Established Program to Stimulate Competitive Research (EPSCoR), a collaborative research team from the University of Maine and the University of Alabama develops, synthesizes, and investigates a new class of perovskite halides for optoelectronics. In this combined theoretical and experimental investigation, the team also evaluates the materials’ stability under ambient environmental conditions. Unlike traditional halides with two to three metal elements, these newly developed perovskite halides consist of five or more principal metal elements in nearly equal concentrations. The workplan features a closed feedback loop between theory and experiment and focuses on materials advancement by performing theoretical predictions, developing synthesis methods, characterizing optoelectronic properties, and evaluating stability under exposure to gases, light, and heat. New perovskite halide materials discovered from this project could lead to a wide variety of optoelectronic applications including solar cells, light-emitting devices, photodetectors and lasers, photoelectrochemical catalysts, radiation detectors, and sensors. This research allows project participants from interdisciplinary programs at these two universities to interact and contribute to technology development within Maine and Alabama. Three Ph.D. graduate students and six undergraduates are trained to acquire skills and competency in the three foundational pillars of computation, experiments, and data analysis which are key attributes for the next-generation workforce. STEM outreach and education activities disseminated to K-12 students, high-school teachers, and the general public within Maine and Alabama are aimed at conveying how collaborative energy-materials design-driven research is relevant to addressing societal challenges. PART 2: TECHNICAL SUMMARYThis project, which is jointly funded by the Solid State and Materials Chemistry program in the Division of Materials Research and the Established Program to Stimulate Competitive Research (EPSCoR), aims to computationally design and experimentally realize a new class of lead-free perovskite halide materials with enhanced thermodynamic and environmental stability along with desired optoelectronic properties. Entropy-stabilized perovskite halides (ESPHs) containing five or more principal metal elements are investigated for enhanced optoelectronic properties and stable environmental performance. The key hypothesis is that the configurational entropy of mixing plays a dominant role in stabilizing a single-phase crystalline ESPH structure. The validation of this hypothesis not only provides a new experimentally controllable pathway to design more stable perovskite halide materials but also yields unique composition-structure-property relationships that are absent when chemical order prevails. Specific objectives are to (i) predict the combinations of metal elements that can give rise to stable ESPHs using high-throughput first-principles calculations, (ii) synthesize the predicted ESPHs using the solid-state solution, hydrothermal, and solvent precipitation methods, (iii) characterize the compositional, structural and optoelectronic properties of the synthesized ESPHs, and (iv) evaluate and analyze the stabilities of experimentally synthesized ESPHs under various laboratory environments including humidity, oxidizing/reducing gases, and heat. New ESPHs from this project are poised to substantially expand the chemical space of perovskite halides, providing more capabilities to tune and tailor materials properties of interest (such as lattice parameter, bandgap, optical absorption strength, and conductivity) and render high potential for a wide variety of optoelectronic applications including solar cells, light-emitting devices, photoelectrochemical catalysts, photodetectors and lasers, radiation detectors, and sensors.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.