2. Studies of nanoscale multivalent(?) lead-free halide double perovskites
Author: Anna Dávid
Co-author: Xianjie Liu
Perovskites are promising candidates for several optoelectronic and perhaps spintronic applications, however one of the biggest roadblocks of development is the lead content of current best performing crystals. In lead-free halide double perovskites (elpasolites) there are two different types of cations inside the halide octahedra alternating through the crystal lattice.
Their low/non-toxicity and tunability re-opened the in-depth studies of fully inorganic double perovskites, and it has been found there are promising candidates for photocatalysts, LEDs, photodetectors, X-ray detectors and maybe even photovoltaics. Several high-throughput density functional calculations predicted their structural stability, however extensive experimental observations are not reported. Our group is focusing on the synthesis and studies of some examples from this great branch of materials.
Among several characterization techniques we employ X-rays (XAFS, XPS, XRD) to study the composition and structure of double perovskites with the Cs2NaBCl6 (Cs2NaFeCl6[1,2,3], Cs2NaVCl6) stoichiometry, where B is theoretically a trivalent cation. Using these methods, we are searching for direct evidence on valences and their contribution to the magnetic and optical properties.
 Ji, F. (2021), Bandgap Engineering of Lead-Free Halide Double Perovskites [Doctoral Thesis]
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 Cao, X. et al. (2019), ACS Applied Materials & Interfaces 11 (42), 38648-38653