Interplay of static and dynamic disorder in the mixed-metal chalcohalide Sn₂SbS₂I₃

Abstract

Chalcohalide mixed-anion crystals have seen a rise in interest as ‘perovskite-inspired materials’ with the goal of combining the ambient stability of metal chalcogenides with the exceptional optoelectronic performance of metal halides. Sn₂SbS₂I₃is a promising candidate, having achieved a photovoltaic power conversion efficiency above 4%. However, there is uncertainty over the crystal structure and physical properties of this crystal family. Using a first-principles cluster expansion approach, we predict a disordered room temperature structure, comprising both static and dynamic cation disorder on different crystallographic sites. These predictions are confirmed using single-crystal X-ray diffraction. Disorder leads to a lowering of the bandgap from 1.8 eV at low temperature to 1.5 eV at the experimental annealing temperature of 573 K. Cation disorder tailors the bandgap, allowing for targeted application for this class of materials in optoelectronics.

Lead-Free Semiconductors: Phase-Evolution and Superior Stability of Multinary Tin Chalcohalides

“…The observed inhomogeneous broadening is consistent with the presence of significant structural disorder, giving support to recent crystallographic models of Sn 2 SbS 2 I 3 which exhibit multiple S and I positions as well as Sn and Sb site mixing. 21 Moving down to the heavier pnictide (Pn), the crystal structure of Sn 2 BiS 2 I 3 shows two unique Sn sites, one of which exhibits mixed Pn occupancy (50% Sn:50% Bi). Similar 119 Sn NMR line widths were observed for Sn 2 SbS 2 I 3 and Sn 2 BiS 2 I 3 .…”

Screening Mixed-Metal Sn2M(III)Ch2X3 Chalcohalides for Photovoltaic Applications

“…80 In addition, we also included in our search the DCGAT-3 data set by Schmidt et al, which was used to train their thirdgeneration crystal-graph attention network and includes about 3.18 million crystalline compounds, including a large number of quaternary materials. Nicolson et al, 17 which provides us with an opportunity to validate our computational approach. Our PBEsol results for the energy differences between the Cmc2 1 and P2 1 /c phases and the Cmcm phase are reported in Table 1 and are in good agreement with the optB86b-vdW results of Kavanagh and Nicolson.…”

“…16,18−22 changes to a monoclinic P2 1 /c structure below 100 K. 21 This P2 1 /c structure was then shown to be lower in energy than the Cmcm and Cmc2 1 phases for Sn 2 SbS 2 I 3 by DFT. 17 In addition, for Sn 2 SbS 2 I 3 , UV−vis absorption spectroscopy and DFT calculations revealed that the optical band gap lies below 1.5 eV. 11,12,23 This limits its applications to single-junction solar cells as the band gap is close to the optimum value of harvesting solar radiation (1.3 eV).…”

“…12 This is a promising start considering that the first perovskite solar cells only reached a PCE of 3.8% in 2009 14 and now exceed 25%. 15 Over the past four decades, the M(II) 2 M(III)Ch 2 X 3 material space�lead-free as well as lead-based�has only scarcely been explored (both theoretically and experimentally), and only a few compounds are known such as Sn 2 SbS 2 I 3 , 11,12,16,17 Sn 2 SbSe 2 I 3 , 18 Sn 2 BiS 2 I 3 , 19 Pb 2 SbS 2 I 3 , 20−22 and Pb 2 BiS 2 I 3 . 19,22 X-ray diffraction (XRD) revealed that M(II) 2 M(III)Ch 2 X 3 materials crystallize predominantly in an orthorhombic Cmcm space group.…”

Exploring Chalcohalide Perovskite-Inspired Materials (Sn2SbX2I3; X = S or Se) for Optoelectronic and Spintronic Applications

“…12 Among them, chalcohalide PIMs have emerged as promising materials having an ns 2 electronic configuration as well as a cation−halide combination. 11,13,14 Recently, Nie et al 13 have synthesized a solar cell based on tin−antimony sulfoiodide (Sn 2 SbS 2 I 3 ) using a single-step, solution-based chemical deposition process, exhibiting a power conversion efficiency (PCE) of 4.04%. They have also demonstrated its stability against air, moisture, and light illumination.…”