Luminescent 3D chiral hybrid metal-halide perovskites for piezoelectric energy harvesting and ultrasound detection

Abstract

Hybrid metal-halide perovskites (HMHPs) have received extraordinary attention due to their remarkable application potential in next-generation photoelectric devices. However, three-dimensional (3D) lead-free halide perovskites with piezoelectrics are rare. Here, we report the synthesis of a pair of chiral 3D piezoelectric HMHPs, [(R)-(+)-3-aminoquinuclidine]RbI₃ and [(S)-(−)-3-aminoquinuclidine]RbI₃ [(R-3AQ)RbI₃ and (S-3AQ)RbI₃], which exhibit a reversible order–disorder phase transition with temperature and near-yellow photoluminescence emission under ultraviolet irradiation. Theoretical calculations demonstrate that (R-3AQ)RbI₃ possesses a direct bandgap electronic structure, relatively low elastic properties, and large piezoelectric strain coefficients. The d₁₄ value (14.54 pC N⁻¹) is approximately 20 times larger than that of quartz crystals. Additionally, a polycrystalline film device of (R-3AQ)RbI₃ was fabricated, which shows favorable performance for piezoelectric energy harvesting. More importantly, this device exhibits exceptional underwater ultrasound detection performance, attributed to the low acoustic impedance (2.68–6.15 MRayl) of (R-3AQ)RbI₃, which matches well with water (1.5 MRayl). This work opens up new avenues for utilizing 3D chiral lead-free halide perovskites in electromechanical sensing applications.

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New concepts

Hybrid metal-halide piezoelectrics can be effectively constructed by incorporation of chiral organic cations. However, these chiral hybrid metal-halides always only possess suboptimal longitudinal piezoelectric coefficients or shear piezoelectricity, which limits their applications in electromechanical conversion. To utilize the shear piezoelectricity, a polycrystalline film device was fabricated based on our reported chiral hybrid metal-halide perovskite. Compression occurs among grain boundaries when the crystal film is subjected to stress, resulting in a piezoelectric response that is perpendicular to the crystal film and easily detectable. Notably, this device exhibits favorable performance in energy harvesting and underwater ultrasound detection.

Introduction

Hybrid metal-halide perovskites (HMHPs) have garnered significant attention in the field of materials chemistry. Their unique architecture and composition endow them with fascinating physical properties, such as semiconductivity, photoelectricity, piezoelectricity, and ferroelectricity, which present enormous potential for applications in solar cells, light-emitting diodes, lasers, sensing, and so on.^1–10 The general chemical formula of three-dimensional (3D) HMHPs is ABX₃, where A, B, and X represent organic amine cations, metal ions, and halide anions that coordinate with B, respectively. Owing to the rich selectivity of A-, B-, and X-sites, HMHPs exhibit an unprecedented degree of chemical and structural variabilities.¹¹ Over the past two decades, significant efforts have been devoted to developing various HMHPs, particularly A^IB^IIX₃-type metal halide perovskites.^12–14 Hybrid lead halide perovskites have been recognized as promising materials for high-efficiency photovoltaic and optoelectronic applications.^15–18 Nevertheless, the incorporation of the toxic lead element in these intriguing perovskites imposes significant limitations on their applications. Environmentally benign tin- and germanium-based halide perovskites also exhibit impressive properties in optoelectronic applications, but their stability presents a significant challenge.^19–21 To address the above dilemma, A^IIB^IX₃-typed lead-free halide perovskites have been developed, where the divalent B-site is replaced for monovalent alkali ions and monovalent organic amine cations are substituted for divalent ones.²² Meanwhile, the incorporation of strongly ionic alkali ions remarkably expands their bandgap (>3 eV), which far exceeds the ideal values (1–1.5 eV) for optoelectronic applications.^23,24 However, alkali-based HMHPs also offer great opportunities for the development of other physical properties and applications, such as ferroelectricity and piezoelectricity.^25,26

The structural symmetry of HMHPs is highly susceptible to the configuration of organic cations; therefore, introducing chiral or polar divalent organic molecules into the perovskite framework can enable the efficient construction of compounds with ferroelectricity and piezoelectricity.²⁷ For instance, 3-ammoniopyrrolidinium (AP) has been employed as a model to assemble a 3D perovskite ferroelectric: [(AP)RbBr₃], which possesses a high Curie temperature and excellent thermal stability.²⁸ Despite considerable efforts, studies on alkali-based perovskite ferroelectrics and piezoelectrics as well as their applications remain scarce. In this work, we report the synthesis and structure of a pair of enantiomeric 3D chiral alkali-based HMHPs, (R-3AQ)RbI₃ [R-3AQ, (R)-(+)-3-aminoquinuclidine] and (S-3AQ)RbI₃ [R-3AQ, (S)-(−)-3-aminoquinuclidine]. Furthermore, we comprehensively investigated their phase transition behavior, optical properties, electronic structure, elastic properties, and piezoelectric properties by experimental and theoretical methods. More importantly, we fabricate a polycrystalline film device based on (R-3AQ)RbI₃ crystals and explore its electromechanical sensing, including piezoelectric energy harvesting and ultrasound detection.

Results and discussion

Crystal structure and phase transition

Both (R-3AQ)RbI₃ and (S-3AQ)RbI₃ crystallize in the trigonal chiral space group P3₁21 at low-temperature (LTP) (Table S1, ESI†). The cell parameters for (R-3AQ)RbI₃ and (S-3AQ)RbI₃ are a = b = 10.0749/10.0786 Å, c = 25.0784/25.1161 Å, and V = 2204.5/2209.4 ų. Our results indicate that both compounds possess a typical perovskite structure at room temperature. In the structures, each Rb⁺ coordinates with adjacent six I⁻ to constitute an RbI₆ octahedron. These octahedra further expand into the perovskite framework, while the perovskite cavity is occupied by the protonated R/S-3AQ²⁺ cations, as shown in Fig. 1a and b. The Rb–I bond lengths range from 3.521 to 3.672 Å. It is noteworthy that the cations are fully ordered in the LTP. Meanwhile, R/S-3AQ²⁺ cations interact strongly with the [RbI₃]²⁻ framework through N–H⋯I hydrogen bonds (Fig. S1, ESI†). The H⋯I distances range from 2.647 to 3.266 Å. The strong hydrogen bonding interactions between the [RbI₃]²⁻ framework and the organic cations can be confirmed by Hirshfeld surface theory calculations.²⁹ The calculated Hirshfeld surfaces of the R-3AQ²⁺ cations are illustrated in Fig. S2 (ESI†), in which the red regions represent the relatively strong interactions and the blue regions indicate weak ones. Notably, several red regions can be observed, corresponding to different N–H⋯I hydrogen bonds. Furthermore, powder X-ray diffraction (XRD) experiments were performed to verify the phase purity of (R/S-3AQ)RbI₃ samples (Fig. 2a). To ascertain the chirality of (R-3AQ)RbI₃ and (S-3AQ)RbI₃, their circular dichroism (CD) spectra were collected (Fig. 2b). The mirror cotton effect confirms that these two compounds exhibit CD signals with identical peaks but opposite directions, suggesting that the chirality has been transferred from organic cations to the whole structure.

Fig. 1 3D packing structure of LTP and HTP of (R-3AQ)RbI₃ (a) and (c) and (S-3AQ)RbI₃ (b) and (d). Color codes: Rb, green; N, blue; I, violet; C, gray; and H, white.

Fig. 2 (a) Powder XRD patterns and (b) circular dichroism spectra of (R-3AQ)RbI₃ and (S-3AQ)RbI₃ at room temperature. (c) and (d) DSC curves as a function of temperature of (R-3AQ)RbI₃ and (S-3AQ)RbI₃, respectively.

To gain insight into their thermal behavior, differential scanning calorimetry (DSC) experiments of (R/S-3AQ)RbI₃ were conducted, as shown in Fig. 2c and d. The DSC results unambiguously reveal that both compounds undergo a reversible structure transition. The phase transition temperatures are approximately 446.1 and 415.1 K for (R-3AQ)RbI₃ and 446.3 and 428.5 K for (S-3AQ)RbI₃ during heating and cooling, respectively. These sharp endothermic and exothermic peaks, along with the large thermal hysteresis (31.0 and 15.8 K), demonstrate that the phase transitions of both compounds are typical first-order transitions.³⁰ The evaluated entropy changes (ΔS) across the transition during heating and cooling for (R-3AQ)RbI₃ and (S-3AQ)RbI₃ are 24.15 and 21.90 J mol⁻¹ K⁻¹ and 28.66 and 25.22 J mol⁻¹ K⁻¹, respectively (Fig. S3, ESI†). These large ΔS values indicate that drastic dynamic reorientations occur across the phase transitions for both compounds. To further confirm the phase transition behavior of the two compounds, single-crystal XRD data were collected at 465 K. At 465 K (high-temperature phase, HTP), the chirality of (R/S-3AQ)RbI₃ disappears, turning to the centrosymmetric cubic system with a Pm3̄m space group. The cell parameters are a = b = c = 7.3138/7.3079 Å and V = 391.22/391.08 ų. At this temperature, the pseudo-cubic perovskite framework in the LTP converts to a standard cubic perovskite framework, while the R/S-3AQ²⁺ cations exhibit a completely disordered state, as shown in Fig. 1c and d, which is consistent with the DSC experiments.

Optical properties and electronic structure

Next, the optical properties of (R-3AQ)RbI₃ were investigated. The UV-vis absorption spectrum indicates that (R-3AQ)RbI₃ exhibits visible absorptions at 236, 297, and 373 nm (Fig. 3a). The photoluminescence (PL) experimental results demonstrate that (R-3AQ)RbI₃ displays near yellow emission centered at 546 nm, corresponding to the CIE coordinates at (0.39, 0.59), with a full width at half maximum (FWHM) of 72 nm under 330 nm irradiation (Fig. 3a and b). The PL excitation–emission matrix spectra indicate that (R-3AQ)RbI₃ exhibits a single emission color under different excitation wavelengths, as shown in Fig. 3c. Additionally, the time-resolved luminescence spectrum shows that the average lifetime of (R-3AQ)RbI₃ is only 1.46 ns, suggesting the nature of PL emission (Fig. 3d).

Fig. 3 (a) Emission and UV-vis absorption spectra, (b) CIE chromaticity coordinates, (c) photoluminescence excitation–emission matrix spectra, (d) the decay curves and calculated PL lifetimes, (e) calculated electronic band structure, and (f) partial density of states for (R-3AQ)RbI₃. Inset in (a): photos of crystals before and after UV excitation.

To probe the luminescence mechanism of (R-3AQ)RbI₃, density functional theory (DFT) calculations were performed based on its LTP phase. The obtained electronic band structure and the partial density of states (PDOS) are displayed in Fig. 3e and f. It can be observed that (R-3AQ)RbI₃ possesses a direct bandgap structure at the Γ point in the Brillouin zone with a bandgap value of 3.85 eV, which aligns with the experimentally estimated value of 3.57 eV obtained from the Tauc plot (Fig. S4, ESI†). The PDOS results show that the valence band maximum (VBM) of (R-3AQ)RbI₃ is mainly determined by the I-5p orbital, together with minor orbital contributions from the states of Rb-4s, Rb-4p, and I-5s. For the conduction band minimum (CBM), the primary contributions originate from the states of I-5s and Rb-4p, with insignificant contributions from Rb-4s and R-3AQ²⁺ states. Overall, the PL emission of (R-3AQ)RbI₃ is dominated by the I⁻ electron transitions.

Elastic and piezoelectric properties

The elastic properties of crystals play a crucial role in understanding their piezoelectric properties and evaluating fatigue behavior in operational scenarios.³¹ Given the mirror symmetry exhibited by (R-3AQ)RbI₃ and (S-3AQ)RbI₃, (R-3AQ)RbI₃ was chosen as a representative for an in-depth analysis of its elastic properties. The elastic constants (C_ij) and bulk modulus (K) of (R-3AQ)RbI₃ were calculated using the DFT method. Based on the C_ij, Young's modulus (E), shear modulus (G), and Poisson's ratio were deduced, as presented in both 3D and two-dimensional (2D) representations (Fig. 4a–d and Fig. S5, ESI†). The maximum and minimum values for these elastic parameters are listed in Table S2 (ESI†). The 3D and 2D plots of E are displayed in Fig. 4a and b. The regular contour with arc-shaped corners along different directions indicates the low elastic anisotropy of E for (R-3AQ)RbI₃, which is in accord with its highly symmetrical framework. The maximum value of Young's modulus (E_max) is along the 〈02−1〉 direction with a value of 18.37 GPa, while the minimum value (E_min) is 10.86 GPa along the 〈21−1〉 direction, resulting in an elastic anisotropy value (A_E = E_max/E_min) of 1.69. The Young's modulus of (R-3AQ)RbI₃ is slightly lower than that of the isostructural (R-3AQ)KI₃,³² which may be attributed to decreased coordinate bonds and hydrogen bond interactions. For shear modulus, the 3D and 2D plots are presented in Fig. 4c and d. The maximum value (G_max) is 7.70 GPa along the 〈11−1〉 direction with the shearing of the (−110) plane, which is slightly larger than that of [C₆H₁₄N₂]KBr₃.³³ The minimum value (G_min) is 4.05 GPa, reached in the 〈01−1〉 direction when the (100) plane is sheared. These two values yield an anisotropy value (A_G = G_max/G_min) of 1.90.

Fig. 4 3D and 2D representations of (a) and (b) Young's moduli, (c) and (d) shear moduli, and (e) and (f) piezoelectric strain tensors of (R-3AQ)RbI₃.

Subsequently, the Poisson's ratios of (R-3AQ)RbI₃ are considered, with the 3D and 2D views displayed in Fig. S5a and b (ESI†). Its Poisson's ratios are in the range of 0.097–0.483, resulting in an anisotropy value of 4.98. The sound velocities (c) related to the elastic properties of (R-3AQ)RbI₃ were further investigated, with the resultant 3D and 2D plots shown in Fig. S5c and d (ESI†). The different types of sound velocities of (R-3AQ)RbI₃ range from 1.0 to 2.3 km s⁻¹, which is similar to the values of (R-3AQ)KI₃.³² Its relatively low sound velocities suggest that (R-3AQ)RbI₃ would possess excellent acoustic matching performance when applied in aqueous media and biological tissue.³⁴ Finally, the obtained bulk modulus of (R-3AQ)RbI₃, reflecting its volume compressibility, is 9.98 GPa, which is lower than the value of 14.05 GPa for (R-3AQ)KI₃ due to the decrease in coordinate bonds.³² Overall, (R-3AQ)RbI₃ possesses relatively lower elastic moduli compared to inorganic materials, which could facilitate deformation and induce substantial piezoresponses owing to its space group belonging to the 32-point group that is piezoelectric.³⁵

To quantify the piezoelectricity of (R-3AQ)RbI₃, the piezoelectric strain tensors d_ij were calculated, and the 3D and 2D views are displayed in Fig. 4e and f. The results demonstrate that the (R-3AQ)RbI₃ crystal possesses only two shear piezoelectric coefficients (d₁₁ and d₁₄) with values of −4.04 and 14.54 pC N⁻¹, respectively. The absolute value of d₁₁ is approximately 1.75 times larger than that of quartz single crystals (d₁₁ = 2.31 pC N⁻¹).³⁶ Notably, the d₁₄ is nearly 20 times larger than the value of quartz crystals (d₁₄ = 0.73 pC N⁻¹).

Electromechanical sensing applications

The relatively low elastic moduli and large piezoelectric coefficients demonstrate that (R-3AQ)RbI₃ has great potential for applications in energy conversion. To utilize its shear piezoelectricity, a polycrystalline film of (R-3AQ)RbI₃ was prepared on a PET substrate using the drop-coated method (Fig. 5a). When stress is applied to the polycrystalline film, compression occurs at the grain boundaries, resulting in a piezoelectric voltage perpendicular to the film, which cannot be achieved by organic composite films.³⁷ The powder XRD pattern reveals that the polycrystalline film primarily exposes the (012), (022), (024), and (028) crystal planes (Fig. 5b). To investigate the performance of such a film in energy harvesting and ultrasound detection, a simple sensing device was prepared, with the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer and copper tape as top and bottom electrodes, respectively, and encapsulated with polyimide (PI) tape, as shown in Fig. 5c. This device exhibits significant piezoelectric signals under light tapping with fingers, with an output voltage of about 0.8 V (Fig. 5d), indicating that this polycrystalline film device possesses good sensitivity to macroscopic mechanical forces, making it suitable for energy harvesting applications.

Fig. 5 (a) The preparation process and an optical micrograph of the (R-3AQ)RbI₃ polycrystalline film. (b) XRD patterns of the polycrystalline film and PET substrate compared with the simulated pattern. (c) Schematic representation of the polycrystalline film device construction. (d) Piezoelectric responses of the (R-3AQ)RbI₃ film device lightly tapping with fingers. (e) Characteristic signals were obtained from the (R-3AQ)RbI₃ film device when subjected to ultrasound stimulation (10 MHz) at different distances (3, 6, 9, and 12 mm).

Since ultrasound waves are also a mechanical force, they can also induce strain in piezoelectric crystals, resulting in piezoresponses.³⁸ To probe the detectability of microscopic mechanical forces by this (R-3AQ)RbI₃ device, underwater ultrasonic detection experiments were conducted. Fig. 5e shows the detected signals of this device at different distances when subjected to ultrasound with a frequency of 10 MHz, revealing that the thin film device effectively converts ultrasound into electrical signals. When the distance between the ultrasound source and the device is 3 mm, the signal intensity (V_p–p) is 68.5 mV. Additionally, the detected signal gradually decreases as the distance increases owing to the energy dissipation of ultrasound waves during travel, indicating that the film device can record the position of the ultrasound source. The favorable ultrasound detection performance of (R-3AQ)RbI₃ can be attributed to its low acoustic impedance (Z). Using the equation Z = ρ·c (where ρ and c are the density and sound velocities of the material),³⁹ the calculated Z of (R-3AQ)RbI₃ is 2.68–6.16 MRayl. The compatibility of Z with water (1.5 MRayl) reduces energy dissipation and excessive reflection of ultrasound, thereby improving the efficiency of electromechanical conversion for this device.

Conclusions

In summary, two chiral 3D HOIPs, (R-3AQ)RbI₃ and (S-3AQ)RbI₃, were synthesized and structurally characterized. Both compounds exhibit remarkable first-order phase transition with temperature owing to the dynamic rotation of R/S-3AQ²⁺ cations. Our optical measurements reveal that (R-3AQ)RbI₃ shows near-yellow photoluminescence centered on 546 nm with a low carrier lifetime of 1.28 ns. The first-principles calculations demonstrate that (R-3AQ)RbI₃ belongs to a direct bandgap semiconductor and its PL emission is dominated by the I⁻ electron transitions. Notably, (R-3AQ)RbI₃ possesses relatively lower elastic moduli and sound velocities as well as large shear piezoelectric coefficients. The d₁₄ value is approximately 20 times larger than that of quartz crystals. Furthermore, a polycrystalline film device of (R-3AQ)RbI₃ was fabricated to utilize its shear piezoelectricity, which shows good piezoelectric energy harvesting properties. More importantly, this device presents favorable underwater ultrasound energy transfer performance. The intensity of received signals gradually decreases with increasing distance between the device and the ultrasound source, suggesting that this device can effectively detect the microscopic mechanical forces. This work opens up new avenues for utilizing 3D chiral lead-free HMHPs in energy harvesting and ultrasound detection applications.

Author contributions

K. L., Y.-Q. C. and Y.-J. G. did the material synthesis, characterization studies and experiments. Z.-G. L. performed the first principles calculation. K. L., Y.-J. G. and W. L. wrote the manuscript and revised the manuscript. Y.-J. G., and W. L. supervised the project direction, including experimental and theoretical investigations in this study. All authors discussed the results and commented on the manuscript.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 22375105), the Natural Science Foundation for Young Scientists of Shanxi Province (No. 202203021222293), and the Jinzhong University “1331 project” Collaborative Innovation Center (No. jzxyxtcxzx202105).

References

1. Y. Liu, F. Di Stasio, C. Bi, J. Zhang, Z. Xia, Z. Shi and L. Manna, Adv. Mater., 2024, 36, 2312482.
2. C. Zhang, L. K. Ono and Y. Qi, Adv. Funct. Mater., 2024, 34, 2314762.
3. W. Tang, S. Liu, G. Zhang, Z. Ren, Z. Liu, M. Zhang, S.-Y. Zhang, C. Zou, B. Zhao and D. Di, Adv. Mater., 2024, 2411020.
4. X. Zhang, H. Huang, C. Zhao and J. Yuan, Chem. Soc. Rev., 2025, 54, 3017–3060.
5. H. Dong, C. Zhang, X. Liu, J. Yao and Y. S. Zhao, Chem. Soc. Rev., 2020, 49, 951–982.
6. F. Furlan, J. M. Moreno-Naranjo, N. Gasparini, S. Feldmann, J. Wade and M. J. Fuchter, Nat. Photonics, 2024, 18, 658–668.
7. G. Long, R. Sabatini, M. I. Saidaminov, G. Lakhwani, A. Rasmita, X. Liu, E. H. Sargent and W. Gao, Nat. Rev. Mater., 2020, 5, 423–439.
8. H. Li, Z. Wang, Q. Guan, C. Ji, R. Li, H. Ye, Z. Wu, C. Zhang and J. Luo, Angew. Chem., Int. Ed., 2025, e202500765.
9. L. N. Quan, B. P. Rand, R. H. Friend, S. G. Mhaisalkar, T.-W. Lee and E. H. Sargent, Chem. Rev., 2019, 119, 7444–7477.
10. H. Zhang, Z.-K. Xu, Z.-X. Wang, H. Yu, H.-P. Lv, P.-F. Li, W.-Q. Liao and R.-G. Xiong, J. Am. Chem. Soc., 2023, 145, 4892–4899.
11. Y. Wang, Y. Wang, T. A. S. Doherty, S. D. Stranks, F. Gao and D. Yang, Nat. Rev. Chem., 2025, 9, 261–277.
12. W. Li, Z. Wang, F. Deschler, S. Gao, R. H. Friend and A. K. Cheetham, Nat. Rev. Mater., 2017, 2, 16099.
13. W. Xu, Q. Hu, S. Bai, C. Bao, Y. Miao, Z. Yuan, T. Borzda, A. J. Barker, E. Tyukalova, Z. Hu, M. Kawecki, H. Wang, Z. Yan, X. Liu, X. Shi, K. Uvdal, M. Fahlman, W. Zhang, M. Duchamp, J.-M. Liu, A. Petrozza, J. Wang, L.-M. Liu, W. Huang and F. Gao, Nat. Photonics, 2019, 13, 418–424.
14. L.-C. An, K. Li, Z.-G. Li, S. Zhu, Q. Li, Z.-Z. Zhang, L.-J. Ji, W. Li and X.-H. Bu, Small, 2021, 17, 2006021.
15. W. Zhang, G. E. Eperon and H. J. Snaith, Nat. Energy, 2016, 1, 16048.
16. J. Jeong, M. Kim, J. Seo, H. Lu, P. Ahlawat, A. Mishra, Y. Yang, M. A. Hope, F. T. Eickemeyer, M. Kim, Y. J. Yoon, I. W. Choi, B. P. Darwich, S. J. Choi, Y. Jo, J. H. Lee, B. Walker, S. M. Zakeeruddin, L. Emsley, U. Rothlisberger, A. Hagfeldt, D. S. Kim, M. Grätzel and J. Y. Kim, Nature, 2021, 592, 381–385.
17. M. Simenas, A. Gagor, J. Banys and M. Maczka, Chem. Rev., 2024, 124, 2281–2326.
18. X. Dong, Y. Shen, F. Wang, Z. He, Y. Zhao, Z. Miao and Z. Wu, Small, 2025, 2412809.
19. H. Liu, Z. Zhang, W. Zuo, R. Roy, M. Li, M. M. Byranvand and M. Saliba, Adv. Energy Mater., 2023, 13, 2202209.
20. W. Gao, R. Huang, H. Dong, W. Li, Z. Wu, Y. Chen and C. Ran, Chem. Soc. Rev., 2025, 54, 1384–1428.
21. J. Jin, Z. Zhang, S. Zou, F. Cao, Y. Huang, Y. Jiang, Z. Gao, Y. Xu, J. Qu, X. Wang, C. Chen, C. Xiao, S. Ren and D. Zhao, Adv. Energy Mater., 2024, 2403718.
22. L. A. Paton and W. T. A. Harrison, Angew. Chem., Int. Ed., 2010, 49, 7684–7687.
23. W. Li, A. Stroppa, Z. Wang and S. Gao, Hybrid Organic–Inorganic Perovskites, John Wiley & Sons, 2020, ch. 1, pp. 1–13.
24. Z. Deng, F. Wei, F. Brivio, Y. Wu, S. Sun, P. D. Bristowe and A. K. Cheetham, J. Phys. Chem. Lett., 2017, 8, 5015–5020.
25. S. D. Mahapatra, P. C. Mohapatra, A. I. Aria, G. Christie, Y. K. Mishra, S. Hofmann and V. K. Thakur, Adv. Sci., 2021, 8, 2100864.
26. L. Xin, Z. Zhang, M. A. Carpenter, M. Zhang, F. Jin, Q. Zhang, X. Wang, W. Tang and X. Lou, Adv. Funct. Mater., 2018, 28, 1806013.
27. H.-Y. Liu, H.-Y. Zhang, X.-G. Chen and R.-G. Xiong, J. Am. Chem. Soc., 2020, 142, 15205–15218.
28. Q. Pan, Z.-B. Liu, Y.-Y. Tang, P.-F. Li, R.-W. Ma, R.-Y. Wei, Y. Zhang, Y.-M. You, H.-Y. Ye and R.-G. Xiong, J. Am. Chem. Soc., 2017, 139, 3954–3957.
29. D. J. Carter, P. Raiteri, K. R. Barnard, R. Gielink, M. Mocerino, B. W. Skelton, J. G. Vaughan, M. I. Ogden and A. L. Rohl, CrystEngComm, 2017, 19, 2207–2215.
30. W. Zhang and R.-G. Xiong, Chem. Rev., 2012, 112, 1163–1195.
31. K. Li, Y. Qin, Z.-G. Li, T.-M. Guo, L.-C. An, W. Li, N. Li and X.-H. Bu, Coord. Chem. Rev., 2022, 470, 214692.
32. K. Li, Z.-G. Li, B. Zhang, Y.-Q. Chen, H. Cao and W. Li, APL Mater., 2023, 11, 031110.
33. M. Azeem, H. Zhang, L.-J. Ji, L.-Y. Dong, P.-X. Lu and W. Li, Chin. J. Struct. Chem., 2020, 39, 174–181.
34. T.-M. Guo, F.-F. Gao, Z.-G. Li, Y. Liu, M.-H. Yu and W. Li, APL Mater., 2020, 8, 101106.
35. M. de Jong, W. Chen, H. Geerlings, M. Asta and K. A. Persson, Sci. Data, 2015, 2, 150053.
36. C. Tannous, Eur. J. Phys., 2017, 38, 065502.
37. Y.-J. Gong, L.-C. An, Y. Zhang, C. Zhao, Z.-G. Li, T.-M. Guo, M. He, J. Yu, W. Li and X.-H. Bu, Adv. Funct. Mater., 2024, 34, 2402649.
38. T.-M. Guo, F.-F. Gao, Y.-J. Gong, Z.-G. Li, F. Wei, W. Li and X.-H. Bu, J. Am. Chem. Soc., 2023, 145, 22475–22482.
39. Z.-G. Li, K. Li, L.-Y. Dong, T.-M. Guo, W. Li and X.-H. Bu, Research, 2021, 9850151.

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Footnote

† Electronic supplementary information (ESI) available. CCDC 2434215, 2366228, 2434284 and 2434285. For ESI and crystallographic data in CIF or other electronic format see DOI: https://doi.org/10.1039/d5mh00550g

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