Organic–Inorganic Hybrid Tin Halide Single Crystals with Sulfhydryl and Hydroxyl Groups: Formation, Optical Properties, and Stability

Abstract

Lead (Pb)-free halide hybrid materials have received a great deal of attention because of their potential in optoelectronic applications. However, heteroatom-based amine lead-free tin halide hybrid single crystals have not been well investigated yet. Detailed synthetic processes, growth, crystal structures, and stability of (ACH 2 CH 2 NH 3 ) 2 SnBr 6 (A = OH or SH) and (BCH 2 CH 2 NH 3 ) 2 SnI 4 (B = I or SH) single crystals were investigated. Interestingly, (IH 3 NCH 2 CH 2 SSCH 2 CH 2 NH 3 ) 2 HPO 3 exhibited orange-red photoluminescence (PL) at about 620 nm w i t h a n a v e r a g e P L l i f e t i m e o f a b o u t 9 1 2 n s . (HSCH 2 CH 2 NH 3 ) 2 SnI 4 single crystals exhibited a PL peak at 620 nm with an average PL lifetime of about 0.607 ns. More importantly, (HSCH 2 CH 2 NH 3 ) 2 SnI 4 single crystals exhibited reversible red−black color transformations when exposed to a H 3 PO 2 solution and an ambient atmosphere, which was attributed to oxidation from Sn 2+ to Sn 4+ , rather than from I − to I 3 − (I 2 ). The intriguing characteristics should provide guidance for further optoelectronic applications of these Pb-free halide hybrid materials.

Oxidation-induced phase transformations of hybrid tin bromide single crystals enable the occurrence of second-harmonic generation

“…According to the redox potential (eqn (1)-( 5)) of Sn-Br systems, Sn 2+ is easily oxidized to Sn 4+ in HBr-H 3 PO 2 solution when exposed to ambient atmosphere. [25][26][27] Therefore, the phase transformation phenomenon was easily observed in in situ mother solutions. To investigate the relationship between the reaction concentration and phase transformation rate, solutions of different concentrations were prepared.…”

“…And thus, Sn(II) is very easy to oxidize, which leads to the inevitable formation of Sn(IV) in the sample during XPS measurements. 25,37,38 The Sn(IV) state plays a dominant role in the Sn3d XPS spectra of DMESnBr 6 single crystals. It is almost impossible to observe high-resolution XPS peaks of Sn 2+ at a binding energy of about 486 eV, and no obvious satellite peaks are found, indicating that there exist only Sn(IV) ions in the crystal lattice.…”

“…This is very similar to the band structure of other Sn(IV)-halide based materials. 25,[42][43][44][45] According to some viewpoints, 46 this is because low-dimensional materials are more dispersed than three-dimensional (3D) materials, and there is no corner/edge sharing. And then the number of tin atoms that coordinate with bromine atoms decreases, resulting in the reduction of the size of {SnBr 6 } units, the shortening of Sn-Br bonds, and the strengthening of bond energy.…”

Crystal structure and Hirshfeld surface analysis of 2-bromoethylammonium bromide – a possible side product upon synthesis of hybrid perovskites

“…The high reactivity of aziridine poses a synthetic challenge as it can undergo ring-opening in acidic environments, leading to the formation of perovskites with low periodicity such as (X(CH 2 ) 2 NH 3 ) 2n (BX) 4n (B = Pb, Sn; X = Br, I; Skorokhod et al, 2023;Song et al, 2022;Sourisseau et al, 2007;Lemmerer & Billing, 2010) and 2-bromoethylammonium bromide as a side product. However, these perovskite materials also often manifest physical properties that are as well worth exploring.…”

Reductant Engineering in Stable and High‐Quality Tin Perovskite Single Crystal Growth for Heterojunction X‐Ray Detectors

“…To address the stability of Sn 2+ ions in the precursor solution, the traditional approaches involve an additive of hypophosphorous acid (H 3 PO 2 ) as a reductant in a haloid acid (HX) solution at high temperatures. [8][9][10][11] However, the H 3 PO 2 reductant is limited to complex acid solutions, which contain diverse ion environments, increasing the likelihood of ions entering the perovskite lattice or grain boundaries. Furthermore, hydroiodic acid (HI), acting as an intermediate material, can promote the oxidation process of Sn 2+ in tin iodide perovskites.…”