Solvent‐Induced Bright Emission in Lead‐Free Organic–Inorganic Antimony Bromides with Reversible Transformation

Abstract

Lead‐free low‐dimensional organic–inorganic metal halides have gained increasing attention in a wide range of applications due to their low toxicity, outstanding optical performance, and structural tunability. In this work, a general method of incorporating organic molecule into sodium antimony bromides is introduced. The 1D Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ single crystals exhibit bright yellow and orange emission with PL peaks at 610 and 664 nm, and high photoluminescence quantum yields (PLQYs) of 85% and 60%, respectively. These two compounds can be reversibly converted into each other by the removal and addition of the organic components. Their exceptional luminescent performance enables them to be used as solid‐state phosphors for the fabrication of yellow and orange down‐conversion LEDs. A white LED with a high color rendering index (CRI) of 95 is also fabricated by using Na₃SbBr₆(C₂H₆OS)₆ as the yellow phosphor. The universality of this method is demonstrated by synthesizing other members of this family with diverse A‐groups, including methylammonium (MA) and formamidinium (FA). This work provides an effective strategy for the development of diverse lead‐free and high‐performance organic–inorganic hybrid materials and indicates these organic–inorganic hybrid compounds are promising luminescent materials for lighting or displays.

A series of lead‐free hybrid antimony bromides are synthesized with bright broadband emission. Their PL peaks are in the range of 607–672 nm and the highest efficiency of 86% is achieved for Na₃SbBr₆(C₂H₆OS)₆. Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ can be reversibly transformed into each other by the removal and addition of the organic molecules.

1. Introduction

Solid‐state phosphors are generally regarded to be energy‐saving light sources by using efficient conversion from electricity to lighting with long lifetimes. Most of the current commercial phosphors contain rare‐earth (RE) metals including europium, terbium, and yttrium.^{[ 1 ]} Although these phosphors possess high photoluminescence quantum yield (PLQY) and stability, their synthesis process is energy‐consuming and complex, and the cost and supply of RE elements are critical issues.^{[ 2 ]} Luminescent lead (Pb) halide perovskites have attracted extensive attention in display and lighting‐emitting diodes (LEDs) recently because of their notably strong photoluminescence and good solution processability.^{[ 3 ]} Nevertheless, the extreme toxicity of lead remains a critical issue to be addressed, and lead‐free materials with excellent optical properties are highly desirable.^{[ 4 ]}

Sb(III) has been studied as an attractive candidate for the replacement of Pb because of its similar isoelectronic nature and ns² lone pairs in Sb³⁺ and Pb²⁺ ions and oxidative stability compared with Sn(II) and Ge(II).^{[ 5 ]} Environmentally friendly all‐inorganic Sb‐based compounds Cs₃Sb₂X₉ (X = Cl_xBr_yI_1‐x‐y, 0 ≤x, y ≤1) colloidal quantum dots were synthesized with tunable emission from 370 to 560 nm by anion exchange reactions. A highest photoluminescence quantum yield (PLQY) value of 46% was obtained,^{[ 6 ]} but its stability needed to be further improved for practical applications. Bulk Rb₇Sb₃X₁₆ (X = Cl, Br) with yellow and orange emission were also reported, but their PLQYs were rather low (<4%).^{[ 7 ]} However, the incorporation of organic molecules into the crystal structure of alkali metal halides led to a new understanding of the optical features of hybrid compounds.^{[ 8 ]} Organic–inorganic hybrid Sb‐based materials have been widely investigated because of their combination of unique optical properties and structural flexibility. These hybrid antimony halides usually involved single charged organic cations including Bzmim⁺, Ph₄P⁺, TMA⁺, PMA⁺, etc.^{[ 9 ]} Most of these materials possess [SbX₅]²⁻ clusters with bright emission while [SbX₆]³⁻ octahedra were less reported. Exploring [SbX₆]³⁻ has the potential to deepen our understanding of the relationship between crystal structures and optical properties, reveal the fundamental mechanisms governing their photophysical properties, and provide valuable insights into the development of strategies for designing and exploring more effective optoelectronic devices. Morad et al.^{[ 10 ]} demonstrated a supramolecular strategy to coordinate18‐crown‐6 ether with alkali (K⁺, Rb⁺, Cs⁺) and alkaline metals (Ba²⁺) to control the formation of Sb‐X clusters resulting in changes in emission colors with PL peaks ranging from 550 to 750 nm. Recently, yellow emissive [Na(DMSO)₂]₃SbBr₆ single crystals have been reported to have a PLQY value of 56% by an antisolvent method.^{[ 11 ]}

Herein, we enhance the efficiency of Na₃SbBr₆(C₂H₆OS)₆ single crystals by using a slow cooling down method and further enlarge the diversity of the family of hybrid alkali antimony halides by incorporating organic molecules tetrahydrothiophene 1‐oxide (C₄H₈OS) with sodium antimony bromides. We also demonstrated the synthetic strategy can be further applied to methylammonium (MA) and formamidinium (FA) antimony bromides. The obtained molecule‐capped organic–inorganic hybrid Na₃SbBr₆(L)₆ (L = C₂H₆OS and C₄H₈OS) single crystals feature 1D structures and [SbBr₆]³⁻ octahedra. The yellow emissive Na₃SbBr₆(C₂H₆OS)₆ and orange emissive Na₃SbBr₆(C₄H₈OS)₆ possess high PLQY values of 86% and 59%, respectively, much higher than those of the reported 18‐crown‐6 ether‐capped compounds (11‐45%) possessing [SbBr₆]³⁻ clusters.^{[ 10 ]} It was also observed that the incorporation of organic solvent molecules in the crystals enables them to transform into each other reversibly by the addition and removal of the organic components. Furthermore, yellow and orange LEDs were fabricated by using Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ as phosphors, respectively. And a white‐emitting device with a high color rendering index (CRI) of 95 was demonstrated by using Na₃SbBr₆(C₂H₆OS)₆ as the yellow phosphor. Moreover, MA₃SbBr₆(C₂H₆OS)₂, FA₃SbBr₆(C₂H₆OS)₂, and FASbBr₄(C₄H₈OS)₃ single crystals are obtained with PL peaks of 607, 672, and 663 nm, respectively.

2. Results and Discussion

Na₃SbBr₆(L)₆ (L = C₂H₆OS and C₄H₈OS) single crystals were obtained by the slow cooling down method (see Experimental Section for complete details).^{[ 12 ]} Single crystal X‐ray diffraction (SCXRD) measurements (Figure 1 ; Tables S1–S3, Supporting Information) revealed that Na₃SbBr₆(C₂H₆OS)₆ crystallizes in the triclinic space group of P‐1 while Na₃SbBr₆(C₄H₈OS)₆ possesses trigonal space group of R‐3. The different crystal structures are likely caused by the different rigidity and sizes of organic molecules. In the crystals, each Sb³⁺ cation is coordinated with six Br⁻, forming a [SbBr₆]³⁻ octahedral cluster, the bond lengths of Sb–Br and angles are different in the two compounds (Figure S1, Supporting Information). The neighboring clusters are bridged by [Na₃(L)₆]³⁺ (L = C₂H₆OS and C₄H₈OS) units consisting of unique 1D chains. In [Na₃(L₆)]³⁺ units, µ²‐oxygens of three C₂H₆OS or C₄H₈OS molecules connect the two adjacent sodium atoms. The phase purities of as‐synthesized single crystals were checked by the comparison between experimental powder X‐ray diffraction (PXRD) patterns and simulated SCXRD data (Figure S2, Supporting Information). Fourier transform infrared (FTIR) spectroscopy was carried out to prove the existence of organic molecules C₂H₆OS in Na₃SbBr₆(C₂H₆OS)₆ and C₄H₈OS in Na₃SbBr₆(C₄H₈OS)₆ by the detection of the S–O deformation mode at 1020 and 1007 cm⁻¹, respectively (Figure S3, Supporting Information). Additionally, energy dispersive spectroscopy (EDS) elemental mapping (Figures S4 and S5, Supporting Information) shows the homogeneous distribution of sodium, antimony, bromine, and sulfur elements in crystals, and the atom ratio of Na/Sb/Br was affirmed to be 3:1:6 in good agreement with the stoichiometry of their SCXRD results. We also explored the substitution of Na⁺ for CH₃NH₃ ⁺ (MA⁺) and CH(NH₂)₂ ⁺ (FA⁺) to extend the synthetic possibilities for this system. MA₃SbBr₆(C₂H₆OS)₂ and FA₃SbBr₆(C₂H₆OS)₂ crystallize in the monoclinic space group of C2 and P2₁/c, respectively, in the crystals, each Sb atom and six Br atoms consist of one [SbBr₆]^3‐ octahedron. FASbBr₄(C₄H₈OS)₃ crystallizes in an orthorhombic space group of Pnma, and each Sb atom was connected to four bromine atoms and two oxygen atoms from C₄H₈OS molecules (Figures S6–S8, Tables S5–S9, Supporting Information).

Figure 1.

a) Crystal structure of Na₃SbBr₆(C₂H₆OS)₆. b) Crystal structure of Na₃SbBr₆(C₄H₈OS)₆. Detailed view of the connection between [SbBr₆]³⁻ octahedra and sodiums connected by c) C2H6OS in Na₃SbBr₆(C₂H₆OS)₆ and C4H8OS in d) Na₃SbBr₆(C₄H₈OS)₆.

The needle‐like Na₃SbBr₆(C₂H₆OS)₆ and block‐like Na₃SbBr₆(C₄H₈OS)₆ crystals are transparent under ambient light, upon excited by 365 nm UV lamps, they generated highly yellow and orange emission, respectively (Figure 2 ). The PL and PL excitation (PLE) spectra of the two compounds were measured as shown in Figure 2b. The PL peak of Na₃SbBr₆(C₂H₆OS)₆ is located at 610 nm with a broad full width at half‐maximum (FWHM) of 157 nm, and its excitation spectrum exhibits a peak at 406 nm. Na₃SbBr₆(C₄H₈OS)₆ possesses broadband orange emission (FWHM of 187 nm) with PL maxima at 664 nm and a PLE peak at 420 nm. Their emission efficiencies were measured as well, a high PLQY value of 86% and 59% was achieved for Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆, respectively (Table 1 ). Moreover, time‐resolved PL (TRPL) experiments were conducted to explore their photophysical properties. The PL decay curves of Na₃SbBr₆(L)₆ (L = C₂H₆OS and C₄H₈OS) were fitted by mono‐exponential functions, and the average lifetimes of Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ were estimated to be 2.3 and 1.9 µs, respectively. MA₃SbBr₆(C₂H₆OS)₂, FA₃SbBr₆(C₂H₆OS)₂, and FASbBr₄(C₄H₈OS)₃ exhibits PL maxima at 607, 672, and 663 nm, respectively. (Figures S9–S11, Supporting Information). However, the brightness of these compounds under UV excitation lags far behind the sodium compounds. The PLQY value was 0.8% for MA₃SbBr₆(C₂H₆OS)₂, 2.3% for FA₃SbBr₆(C₂H₆OS)₂, and 6.7% for FASbBr₄(C₄H₈OS)₃, respectively. Additionally, their PL lifetimes (0.45–0.87 µs) are shorter than hybrid sodium antimony bromides (Figure S12, Supporting Information).

Figure 2.

a) Images of Na₃SbBr₆(C₂H₆OS)₆ bulk crystals under ambient light (top) and UV irradiation (bottom). b) Excitation and emission spectra of Na₃SbBr₆(L)₆ (L = C₂H₆OS and C₄H₈OS) bulk crystals. c) Images of Na₃SbBr₆(C₄H₈OS)₆ bulk crystals under ambient light (top) and UV irradiation (bottom). d) Photoluminescence decay of Na₃SbBr₆(L)₆ (L = C₂H₆OS and C₄H₈OS) bulk crystals with the fit to data.

Table 1.

Optical parameters for antimony bromide single crystals.

Material	PLE peak [nm]	PL Peak [nm]	FWHM [nm]	PLQY [%]
Na3SbBr6(C2H6OS)6	406	610	157	86
Na3SbBr6(C4H8OS)6	420	664	187	59
MA3SbBr6(C2H6OS)2	434	607	146	0.8
FA3SbBr6(C2H6OS)2	412	672	208	2.3
FASbBr4(C4H8OS)3	405	663	159	6.7
[Na(DMSO)2]3SbBr6 [ 11 ]	420	608	160	56
[Na(DMSO)2]3SbBr3Cl3 [ 13 ]	420	606	160	90.6

In order to further investigate the origin of the yellow and orange emission, we measured power‐dependent PL spectra of Na₃SbBr₆(L)₆ (L = C₂H₆OS, C₄H₈OS) single crystals. The PL intensities of both compounds increase linearly with the power density (Figure S13, Supporting Information), ruling out the possibility of permanent defects as the origin of the emission.^{[ 14 ]} In general, the emission of most Sb‐based hybrid halides were attributed to triplet self‐trapped excitons (STEs), seldom blue emission observed in these materials resulted from intra‐ligand charge transfer (ILCT) and transition from the singlet STEs to ground state.^{[ 15 ]} We then measured their PL and PLE spectra by using different excitation and emission wavelengths. As shown in Figures S14 and S15 (Supporting Information), the PL and PLE spectra of both two materials show identical shapes and features without shifts, suggesting that the yellow and orange emission originates from the relaxation of the single excited state.^{[ 16 ]} And the single PL peak detected in each compound excited at different wavelengths excludes the ILCT.^{[ 9} , ^{17 ]} Based on the above results, we can postulate that the emission of Na₃SbBr₆(L)₆ likely originates from the triplet STEs of [SbBr₆]³⁻ that were commonly reported for Sb‐based hybrid halides.^{[ 10} , ¹⁵ , ^{18 ]} Transient absorption (TA) spectroscopy was conducted to prove the formation of STEs in Na₃SbBr₆(L)₆ (L = C₂H₆OS, C₄H₈OS) compounds. As shown in Figure S16 (Supporting Information), upon 310 nm laser excitation, a broad photoinduced absorption (PA) across the probe region was observed, which is obvious evidence of STEs in both materials.^{[ 19 ]} The kinetics of STE states for both compounds are plotted in Figure S17 (Supporting Information). The difference in emission between the two compounds is likely caused by the different structural deformation upon excitation because of their different lengths of bonds and angles in [SbBr₆]³⁻octahedra.

High stability is an important criterion for phosphors when considering their practical use. The photostability and air stability of the two materials were evaluated as shown in Figure S18 (Supporting Information). Both of them exhibited excellent photostability stored in the N₂. The emission intensity of Na₃SbBr₆(C₂H₆OS)₆ almost had no change under continuous irradiation for 12 h, and Na₃SbBr₆(C₄H₈OS)₆ could retain 92% PL intensity after the measurement. However, the PL intensities of these two compounds decayed gradually when kept in the air for 120 min, which may be caused by the loss of solvents or the absorption of the water.

Notably, the reversible structural and PL transformation triggered by heating and the addition of the organic molecules was observed in Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆. Specifically, as shown in Figure 3a, after the yellow‐emissive Na₃SbBr₆(C₂H₆OS)₆ powders were heated at 80 °C in nitrogen for 24 h, the C₂H₆OS was removed and evaporated from the crystals and the yellow emission disappeared. ^{[ 19 ]} S1

Figure 3.

a) Images of the luminescent change of Na₃SbBr₆(C₂H₆OS)₆ powders in the reversible phase transition process under UV light at 365 nm. The corresponding PL spectra change of powders during the transition process starting from b) Na₃SbBr₆(C₂H₆OS)₆ and c) Na₃SbBr₆(C₄H₈OS)₆ powders.

Once adding the C₄H₈OS into the non‐emissive powders, the orange emission was observed, which is in correspondence with the emission of Na₃SbBr₆(C₄H₈OS)₆ (Figure 3b). To demonstrate the reversible transformation between the two compounds, the orange‐emissive powders were further heated at 80 °C in nitrogen for 48 h to remove the C₄H₈OS solvent before adding the C₂H₆OS molecules, subsequently, the yellow emission re‐emerged. This reversible structural change was further proved by the XRD analysis (Figure S19, Supporting Information). Thus, the luminescent change arises from the solvent‐induced structural transformation. Similarly, Na₃SbBr₆(C₄H₈OS)₆ powders could reversibly convert into Na₃SbBr₆(C₂H₆OS)₆ with the same steps by changing the molecules (Figure 3c).

The outstanding optical performance and high photostability of these two compounds are desirable for optoelectronic applications. Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ can be used as down‐conversion yellow and orange phosphors for solid‐state lighting. The yellow and orange LEDs were fabricated by packaging Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ in silicone and coated on the commercial UV‐LED (365 nm) chips, respectively. They emitted bright yellow and orange light when operated at 3.3 V, and their PL spectra were detected as shown in Figure 4a,b. Additionally, the white LED was made by using the mixture of Na₃SbBr₆(C₂H₆OS)₆ and the commercial blue phosphor of BaMgAl₁₀O₁₇:Eu²⁺, the bright cool white light can be obtained (Figure 4c), and a high color rendering index (CRI) of 95 was achieved. The corresponding Commission Internationale de l'Eclairage (CIE) chromaticity coordinates were calculated as (0.51, 0.47), (0.57, 0.42) and (0.33, 0.29) for yellow, orange, and white LEDs, respectively (Figure 4d).

Figure 4.

Emission spectra of the fabricated a) yellow LED based on Na₃SbBr₆(C₂H₆OS)₆, b) orange LED based on Na₃SbBr₆(C₄H₈OS)₆, and c) white LED based on the mixture of Na₃SbBr₆(C₂H₆OS)₆ and BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor, inset: photographs of LEDs (off and on). d) CIE coordinates of yellow, orange, and white LEDs.

3. Conclusion

Lead‐free Sb‐based organic–inorganic hybrid Na₃SbBr₆(L)₆ (L = C₂H₆OS and C₄H₈OS) single crystals with 1D chains were grown by the cooling down method using two different solvents. Both Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ have broad emission spectra and long lifetimes. The highly emissive Na₃SbBr₆(C₂H₆OS)₆ exhibits the PL peak at 610 nm with a high PLQY of 86%, while Na₃SbBr₆(C₄H₈OS)₆ possesses orange emission with an emission peak at 664 nm and 59% of PLQY. Moreover, these two compounds can be reversibly transformed into each other with both emission and crystal structure changes by the removal and addition of the organic molecules in crystals. Since they have strong stability when kept in the N₂ under continuous UV irradiation, yellow, orange, and white LEDs were fabricated, suggesting their potential applications in lighting and display. Furthermore, the replacement of Na⁺ with CH₃NH₃ ⁺ (MA⁺) and CH(NH₂)₂ ⁺ (FA⁺) enables to form the yellow‐emissive MA₃SbBr₆(C₂H₆OS)₂, red‐emissive FA₃SbBr₆(C₂H₆OS)₂, and orange‐emissive FASbBr₄(C₄H₈OS)₃ single crystals with different crystal structures.

4. Experimental Section

Materials

NaBr (anhydrous, ≥99.9%, Sigma–Aldrich), SbBr₃ (99.99%, Sigma–Aldrich), methylammonium bromide (MABr, >99.99%, Greatcell Solar Materials), formamidinium bromide (FABr, >99.99%, Greatcell Solar Materials), dimethyl sulfoxide (anhydrous, ≥99.9%, Sigma–Aldrich), tetrahydrothiophene 1‐oxide (97%, Alfa Aesar), toluene (anhydrous, 99.8%, Sigma–Aldrich).

Synthesis of Na₃SbBr₆(L)₆ (L = C₂H₆OS and C₄H₈OS) Single Crystals

The growth of single crystals was achieved by slowly cooling the saturated solution. For the synthesis of Na₃SbBr₆(C₂H₆OS)_6, a stoichiometric mixture of 0.3 mmol NaBr and 0.1 mmol SbBr₃ was dissolved in 0.2 mL dimethyl sulfoxide. The solution was heated under vigorous stirring until the solution became clear. After the complete dissolution, the solution was slowly cooled down to room temperature. Na₃SbBr₆(C₄H₈OS)₆ single crystals were synthesized by simply replacing 0.2 mL dimethyl sulfoxide by 0.25 mL tetrahydrothiophene 1‐oxide using the same method.

Synthesis of MA₃SbBr₆(C₂H₆OS)₂ Single Crystals

MABr (0.9 mmol) and SbBr₃ (0.3 mmol) was dissolved in 0.1 mL dimethyl sulfoxide. The solution was heated under vigorous stirring until complete dissolution, then the solution was slowly cooled down to room temperature.

Synthesis of FA₃SbBr₆(C₂H₆OS)₂ Single Crystals

FABr (0.3 mmol) and SbBr₃ (0.1 mmol) was dissolved in 0.1 mL DMSO to form clear solution, then toluene was added and diffused into the solution.

Synthesis of FASbBr₄(C₄H₈OS)₃ Single Crystals

FABr (0.2 mmol) and SbBr₃ (0.2 mmol) was dissolved in 0.1 mL tetrahydrothiophene 1‐oxide. The solution was heated under vigorous stirring until complete dissolution, then the solution was slowly cooled down to room temperature.

Fabrication of Yellow, Orange, and White LEDs

The thermal‐curable silicone gel was obtained by mixing Silicone Elastomer Base (DOWSIL 184) with Silicone Elastomer Curing Agent (DOWSIL 184) with a volume ratio of 10:1. Yellow and orange LEDs were fabricated by mixing Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ single crystal powders with the prepared thermal‐curable silicone gel in a mass ratio of 1:2 and deposited on commercially available 365 nm UV‐LED chips, respectively. The white LED was fabricated by combing a 365 nm UV LED chip with the yellow phosphor Na₃SbBr₆(C₂H₆OS)₆ and the commercial BaMgAl₁₀O₁₇:Eu²⁺ blue phosphor (mass ratio of 1:18.3).

Characterization

Single crystal data of Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ were collected on a SuperNova, Dual, Cu–K, Atlas diffractometer at 173.00(10) K and 193.00(10) K, respectively. Using Olex2 as the graphical interface,^{[ 20 ]} the structure was solved with the ShelXT^{[ 21 ]} structure solution program using Intrinsic Phasing and the model was refined with version 2014/7 of ShelXL2014/7^{[ 22 ]} using Least Squares minimization. PXRD patterns of all compounds were collected by a PAnalytical X‐ray diffractometer, Model X'pert Pro equipped with a Cu Kα X‐ray tube operating at 40 kV and 30 mA. The PL and PLE spectra of Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ single crystals were obtained by a spectrofluorometer (FS5, EDINBURGH INSTRUMENTS) at room temperature. The PL spectra of reversible transformation between Na₃SbBr₆(C₂H₆OS)₆ and Na₃SbBr₆(C₄H₈OS)₆ powders and LEDs were monitored by Ocean Optics QEPro High Performance Spectrometer. The PLQYs of samples were measured on an absolute quantum yield measurement system with an integrating sphere (SC‐30, EDINBURGH INSTRUMENTS). PL lifetime was measured at room temperature by a spectrofluorometer (FS5, EDINBURGH INSTRUMENTS) using Multi‐Channel Scaling (MCS) module with pulsed µs xenon lamp. The FTIR spectrum was obtained on Vertex 70 Hyperion 1000 spectrometer (Bruker). The SEM images, elemental mapping and compositions were obtained by using JSM‐7100F Scanning Electron Microscopy equipped for energy dispersive X‐ray spectroscopy. Power dependent PL intensity was measured with a spectrometer (Acton Research Spectrapro 500i) with a 150 line mm⁻¹ grating dispersing the PL onto a cooled CCD (Andor Newton EM), the excitation wavelength is 400 nm. Thermogravimetric analyses (TGA) were performed on a TA Instrument Q5000 unit. Samples were loaded into 100 mL PT crucibles and heated with a ramp rate of 5 °C min⁻¹ from room temperature to 800 °C under 25 mL min⁻¹ nitrogen flow.

Conflict of Interest

The authors declare no conflict of interest.

Supporting information

Supporting Information

Li Y., Zhou Z., Xing Z., Ko P. K., Wong K. S., Sung H. H. Y., Williams I. D., Halpert J. E., Solvent‐Induced Bright Emission in Lead‐Free Organic–Inorganic Antimony Bromides with Reversible Transformation. Small Methods 2025, 9, 2400003. 10.1002/smtd.202400003

Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article.