Facile Fabrication of Highly Stable and Wavelength-Tunable Tin Based Perovskite Materials with Enhanced Quantum Yield via the Cation Transformation Reaction

Abstract

Metal halide perovskites have attracted great attention for their superior light energy conversion applications. Herein, we demonstrated a facile synthesis of zero-dimensional Sn2+ perovskite Cs4–x M x SnBr6(M = K+ and Rb+) material through the cation transformation reaction at room temperature. Cs4SnBr6 NCs was mixed with pure metal bromide salts (KBr and RbBr) via the mechanochemical process to successfully synthesize Cs4–x M x SnBr6 perovskite where transformation of Cs to mixed Cs/Rb and mixed Cs/K was achieved. By substituting different cations, the bright fluorescence of the Cs4–x M x SnBr6 was tuned from dim green to greenish-cyan while achieving the photoluminescence (PL) quantum yield of ∼39%. The crystal structure of Sn based perovskite with the substitution of K+ or Rb+ cations was determined by X-ray diffraction (XRD). Moreover, the Cs4–x M x SnBr6 demonstrated superior air stability and exhibited a better photocatalytic activity for CO2 reduction reaction (CO2RR) with high selectivity of CH4 gas with a higher yield rate compared to the pristine Cs4SnBr6 NCs.

General Synthesis of Layered Rare-Earth Hydroxides (RE = Sm, Eu, Gd, Tb, Dy, Ho, Er, Y) and Direct Exfoliation into Monolayer Nanosheets with High Color Purity

“…Rare-earth-based or doped compounds are widely used in various application fields such as phosphors, sensors, display devices, anticounterfeiting, and cryogenic refrigerants, due to their superior optical and magnetic properties. − Recently, layered rare-earth hydroxides (LREHs) with a general formula of RE 8 (OH) 20 A 4 · n H 2 O (RE: rare-earth ion; A: intercalated anion) have emerged as an important family of anion-exchangeable host materials and attracted wide attention. − LREHs consist of positively charged host layers and interlayer moieties such as chloride (Cl – ) and nitrate (NO 3 – ) anions. The positively charged host is derived from a partial replacement of hydroxyl groups (OH – ) by water molecules (H 2 O) in the 8- and 9-coordination of RE 3+ .…”

Stable Lead‐Free Tin Halide Perovskite with Operational Stability >1200 h by Suppressing Tin(II) Oxidation

“…To investigate the intrinsic PL nature of Cs 4 SnBr 6 , time‐resolved PL spectra were recorded under an excitation of 365 nm (Figure 2c), wherein, original Cs 4 SnBr 6 ‐SnBr 2 exhibited a monoexponential decay with an average lifetime of 506 ns. For Cs 4 SnBr 6 ‐SnF 2 crystals, it was observed that the lifetime increased to 741 ns, indicating that the prolonged lifetime implied the passivation of defects and the increase of radiation recombination [24, 27] . For the Sn‐based perovskite, the oxidation of Sn 2+ may generate Sn vacancies, which may serve as defect states to induce serious non‐radiative recombination.…”

“…The broad‐band, strongly Stokes‐shifted emission (Figure 2a and Figure S8), and relatively long radiative lifetimes indicated that the PL emission of Cs 4 SnBr 6 originates from the radiative process of self‐trapped excitons (STEs) recombination (Figure 2g) [18–27] . In zero‐dimensional perovskite, once carriers are photogenerated, excited‐state electrons will be rapidly self‐trapped by the distorted lattice and then release energy by recombination processes, which is the typical light‐emitting mechanism of STEs [28, 29] .…”

“…2) During the subsequent operation, the samples derived from SnX 2 can also be oxidized by oxygen, resulting in tin vacancy defects and rapid decay of light emission [17–23] . Unfortunately, owing to the easily oxidized nature of Sn 2+ , the Sn II ‐based perovskites exhibit extremely low PLQYs, such as CsSnX 3 nanocrystals (PLQY <1 %), Cs 4 SnX 6 (highest PLQY ≈39 %), which is far lower than that of mature CsPbX 3 nanocrystals [19, 20, 24] . Some effective strategies have been proposed to suppress the oxidation of Sn 2+ , such as a stable tin source (SnC 2 O 4 ), [20] extra reducing agents and additives (such as metallic Sn powder, ascorbic acid) [25, 26] .…”

Recent progress and future prospects on halide perovskite nanocrystals for optoelectronics and beyond

“…Meng et al. demonstrated that the A-site cation of lead-free Cs 4 SnBr 6 NCs could be partially substituted via a balling process at room temperature while the pristine Cs 4 SnBr 6 NCs were fabricated using an HI method ( Meng et al., 2021 ). By mixing the Cs 4 SnBr 6 NCs with pure metal bromide salts (KBr and RbBr), the transformation of Cs to mixed Cs/Rb and mixed Cs/K could be readily achieved.…”