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Bandgap Engineering Based on A-site Ions Tuning in Tin Halide Perovskite.

Authors :: Li M
Luo J
He J
Sun T
Li Y
Zhang C
Chu A
Wu J
Jiang J
Cai M
Zhuang X
Source :: Small (Weinheim an der Bergstrasse, Germany) [Small] 2025 Jan 19, pp. e2409546. Date of Electronic Publication: 2025 Jan 19.
Publication Year :: 2025
Publisher :: Ahead of Print
Abstract: Tin-based halide perovskites (ASnX <subscript>3</subscript> ) have garnered substantial interest due to their unique photoelectric properties and environmentally friendly features. The A-site ions tuning strategy has been proven to promote material performance. However, there is a lack of systematic research on the optical properties, lattice structure variation, and band structure evolution in tin-based perovskites when the A-site ions tune from organic to inorganic. Herein, MA <subscript>1-x</subscript> Cs <subscript>x</subscript> SnBr <subscript>3</subscript> and MA <subscript>1-x</subscript> Cs <subscript>x</subscript> SnI <subscript>3</subscript> (0≤x≤1) flakes are synthesized through a one-pot reaction method. By controlling the Cs ratio, a tunable photoluminescence (PL) emission covering a wide range of 560-685 nm can be observed in MA <subscript>1-x</subscript> Cs <subscript>x</subscript> SnBr <subscript>3</subscript> , with bandgap tuned from 1.8 to 2.15 eV, while the PL ranges from 900 to 950 nm with the bandgap 1.2-1.3 eV for MA <subscript>1-x</subscript> Cs <subscript>x</subscript> SnI <subscript>3</subscript> . Besides, the PL intensity of MA <subscript>1-x</subscript> Cs <subscript>x</subscript> SnBr <subscript>3</subscript> significantly enhances with the increasing Cs ratio. First-principles calculations reveal that the octahedron shrinks gradually as the Cs ratio increases. It increases the orbital overlap between Sn and Br and causes a symmetry variation, thus decreasing the bandgap and increasing emission intensity. This work reveals the photophysical mechanism of improved optical properties and bandgap variation in tin-based perovskites, paving the way for their future applications.<br /> (© 2025 Wiley‐VCH GmbH.)