Seán Kavanagh1,Shanti Liga2,Aron Walsh3,David Scanlon4,Gerasimos Konstantatos2
Harvard University1,ICFO–The Institute of Photonic Sciences2,Imperial College London3,University of Birmingham4
Seán Kavanagh1,Shanti Liga2,Aron Walsh3,David Scanlon4,Gerasimos Konstantatos2
Harvard University1,ICFO–The Institute of Photonic Sciences2,Imperial College London3,University of Birmingham4
Due to their quasi-0D / molecular-aggregate type crystal structure, vacancy-ordered double perovskites (VODPs) with the chemical formula A<sub>2</sub>BX<sub>6</sub>, exhibit unusual material properties associated with both zero-dimensional and three-dimensional materials.<sup>1–4</sup> These include low thermal conductivity, high compressibility, and strong exciton binding despite relatively small semiconducting band gaps, making them potential candidates for a range of alternative applications, such as thermoelectrics, white-light emitters/phosphors, photocatalysts, non-linear optics and more.<br/> <br/>In this study, we report a combined experimental and computational investigation on the mixing behavior of cations in this system. Remarkably, we find ultra-low enthalpic costs to cation mixing, resulting in entropy dominance and ideal mixing behavior. This facilitates the room-temperature and low-temperature synthesis of high-entropy materials (high-entropy semiconductors) from these compounds, as demonstrated experimentally by Folgueras et al in <i>Nature</i>, 2023.<sup>5</sup> We elucidate the underlying structural and electronic origins of this facile cation miscibility in these systems, and analyze the resulting optical, thermodynamic and structural changes upon cation mixing.<br/> <br/>Our work demonstrates that vacancy-ordered perovskites present an exciting new class of high-entropy semiconductors, synthesisable at much milder conditions than typical high-entropy materials. Moreover, we elucidate the origins of this behavior, allowing the extraction of general design rules for high-entropy semiconductors with tailored properties.<br/> <br/>1 S. R. Kavanagh, C. N. Savory, S. M. Liga, G. Konstantatos, A. Walsh and D. O. Scanlon, <i>J. Phys. Chem. Lett.</i>, 2022, <b>13</b>, 10965–10975.<br/>2 Y.-T. Huang, S. R. Kavanagh, D. O. Scanlon, A. Walsh and R. L. Z. Hoye, <i>Nanotechnology</i>, 2021, <b>32</b>, 132004.<br/>3 B. Cucco, C. Katan, J. Even, M. Kepenekian and G. Volonakis, <i>ACS Materials Lett.</i>, 2023, <b>5</b>, 52–59.<br/>4 B. Saparov, J.-P. Sun, W. Meng, Z. Xiao, H.-S. Duan, O. Gunawan, D. Shin, I. G. Hill, Y. Yan and D. B. Mitzi, <i>Chem. Mater.</i>, 2016, <b>28</b>, 2315–2322.<br/>5 M. C. Folgueras, Y. Jiang, J. Jin and P. Yang, <i>Nature</i>, 2023, 1–7.<br/>6 S. M. Liga‡ & S. R. Kavanagh‡, A. Walsh, D. O. Scanlon and G. Konstantatos. <i>J. Phys. Chem. C.</i>, 2023