Synthesis, crystal structure and optical properties of the quasi-0D lead-free organic-inorganic hybrid crystal (C6H14N)3Bi2I9·H2O

The organic-inorganic metal halide perovskite materials have remarkable semiconductor and light absorption characteristics. It shows excellent application prospects in the fields of optoelectronics and temperature sensors. In this work, zero-dimensional lead-free (C6H14N)3Bi2I9·H2O single crystals were synthesized by conventional solvothermal reaction. The crystal structure was analyzed using single crystal X-ray diffraction (SXRD). (C6H14N)3Bi2I9·H2O was crystallized in the orthorhombic crystal system with the space group Pmn21. The material is stable for long-term storage under ambient conditions and shows a reversible thermochromic phenomenon. Through ultraviolet–visible–near-infrared (UV–vis–NIR) absorption analysis, the band gap of (C6H14N)3Bi2I9·H2O at room temperature is found to be 2.12 ​eV and it gradually decreases as the temperature increases. This indicates that the thermochromism is probably caused by charge transfer. The response of material to optical signals was also studied and the maximum value of the responsivity (R) and external quantum efficiency (EQE) at 275 ​nm could reach 11 ​mA/W and 2.4%, respectively. It suggests that the material has a potential for applications in photovoltaic devices. The quasi zero-dimensional lead-free single crystals (C6H14N)3Bi2I9·H2O were synthesized by solvothermal reaction, which was crystallized in the orthorhombic crystal system with the space group Pmn21. It shows a reversible thermochromic phenomenon which may be caused by electrons excitation and charge transfer of bismuth (Bi) element with the increase of temperature. [Display omitted] •The new lead-free organic-inorganic hybrid single crystal (C6H14N)3Bi2I9·H2O was synthesized and the crystal structure were analyzed.•(C6H14N)3Bi2I9·H2O crystal has a typical zero-dimensional structure which has ideal structural flexibility.•The (C6H14N)3Bi2I9·H2O has outstanding thermal stability, reversible thermochromic properties and good photoelectric properties.•As the temperature increases, the hyperchromic effect was observed and the band gap decreases significantly.