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Crystal structure and thermochromic behavior of the quasi-0D lead-free organic-inorganic hybrid compounds (C7H9NF)8M4I16 (M = Bi, Sb)



Winnie Wong-Ng, Xiochen Zhao, Yikai Fu, Yunlin Lei, Chao Wang, Wei Zhou, Shouyu Wang, Weifang Liu


Quasi 0-D lead-Free thermochromic organic-inorganic hybrid single crystals (C7H9NF)8M4I16 (M = Bi, Sb) were synthesized by a conventional solvothermal reaction method. The crystal structures were analyzed using single crystal X-ray diffraction (SXRD). Interestingly, as the temperature increases, the (C7H9NF)8M4I16 (M = Bi, Sb) crystals exhibit a peculiar thermochromic phenomenon. In order to explore the phenomenon of thermochromism, temperature dependent ultraviolet−visible-near-infrared (UV−vis−NIR) absorption spectra were measured. The band gaps of (C7H9NF)8Sb4I16 and (C7H9NF)8Bi4I16 at room temperature are 2.34 eV and 2.1 eV, respectively, and they gradually decrease as the temperature increases. On the basis of the ab initio molecular dynamics (AIMD), and the reduction of the band gap at higher temperatures, it is suggested that the occurrence of thermochromism could be caused by the electronic transitions between the organic functional groups and the inorganic clusters, resulting in the red shift of the electron absorption band. The thermochromic characteristics of these low-dimensional organic-inorganic hybrid metal halides will provide alternative materials for smart window temperature sensors, visual thermometers, and daylight control glasses.
Journal of Alloys and Compounds


Thermochromic, Hybrid inorganic organic (C7H9NF)8M4I16 (M = Bi, Sb), Crystal structure, Band gap, Lead-free


Wong-Ng, W. , Zhao, X. , Fu, Y. , Lei, Y. , Wang, C. , Zhou, W. , Wang, S. and Liu, W. (2021), Crystal structure and thermochromic behavior of the quasi-0D lead-free organic-inorganic hybrid compounds (C7H9NF)8M4I16 (M = Bi, Sb), Journal of Alloys and Compounds, [online],, (Accessed May 21, 2024)


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Created December 31, 2021, Updated November 29, 2022