Halide Double Perovskites with a Spin—Identifying Semiconductors with Spin-Polarized Band Structures

Enhancing the performance of photoconversion devices necessitates slowing down the recombination rate of electrons and holes in semiconductors, to facilitate their diffusion to charge-extraction interfaces. Semiconductors with advantageous light absorption properties and slow charge-carrier recombination could be obtained in semiconductors with suitably aligned spin-polarized band structures. Halide double perovskites with the chemical formula A₂BB’X₆ offer significant chemical flexibility [1, 2], enabling the substitution of the B and B’ sites with various combinations of similarly sized open-shell cations. This potentially results in spin-polarized band structures and robust exchange interactions, making double perovskites an interesting platform for controlling charge-carrier recombination via spin.<br/><br/>Our recent research demonstrates that Fe-based double perovskites exhibit low bandgaps and significant spin polarization and can be efficiently synthesized via mechanochemical synthesis [3]. However, while the incorporation of Fe³⁺ leads to a spin-forbidden recombination pathway, it also compromises electron mobility. Here, I will present a systematic high-throughput computational approach for exploring the opto-spintronic properties of halide double perovskites with robust opto-spintronic properties.<br/><br/>I will present our workflow for establishing a comprehensive database of double perovskites, including computationally determined structural parameters, energetically favorable spin states, and spin-polarized density of states, calculated using first-principles density functional theory with the HSE06 hybrid functional. Expanding on previous work [4], we included 3d, 4d, and 5d transition metals, as well as actinides and lanthanides in our high-throughput workflow, resulting in approximately 12,000 compounds predicted to crystallize in the perovskite structure. Additionally, I will discuss how machine-learning aided characterization of this dataset enables us to identify predictors of favorable opto-spintronic properties, paving the way for the rational design of spin-regulated semiconductors with enhanced photoconversion performance.<br/><br/>[1] Wolf, N. R., Connor, B. A., Slavney, A. H. & Karunadasa, H. I. <i>Doubling the Stakes: The Promise of Halide Double Perovskites</i>. Ang. Chem. Int. Ed. 60, 16264–16278 (2021).<br/>[2] Biega, R.-I., Chen, Y., Filip, M. R. & Leppert, L. <i>Chemical Mapping of Excitons in Halide Double Perovskites</i>. Nano Lett. 23, 8155–8161 (2023).<br/>[3] Jöbsis, H. J., Fykouras, K., Reinders, J.W.C., van Katwijk, J., Dorresteijn, J.M., Arens, T., Vollmer, I., Muscarella, L.A., Leppert, L. & Hutter, E.M. <i>Conduction Band Tuning by Controlled Alloying of Fe into Cs2AgBiBr6 Double Perovskite Powders</i>. Advanced Functional Materials, 2306106 (2023).<br/>[4] Singh, U., Klarbring, J., Abrikosov, I. A. & Simak, S. I. <i>Exploring magnetism of lead-free halide double perovskites: A high-throughput first-principles study</i>. Phys. Rev. Mater. 7, 114404 (2023).