Optical properties evaluation of novel lead-free CsCu2Cl2I in different solvents to investigate solvatochromism behaviour

In this work, cesium iodide and copper chloride were dissolved in N,N-dimethylformamide (DMF) to make a novel double halide lead-free metal halide perovskite (DH-LFP), i.e., CsCu 2 Cl 2 I. This was done at room temperature using an anti-solvent precipitation method. Afterwards, powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), infrared spectroscopy (IR), and absorbance spectroscopy have confirmed the chemical and structural analysis of the synthesized DH-LFP. To proceed further, we used photoluminescence spectroscopy (PLS) to check the optical properties in different solvents, such as hexane (Ex = 225 nm, Em = 287 nm), toluene (Ex = 322 nm, Em = NA), chloroform (Ex = 273 nm, Em = 555 nm), dimethylformamide (Ex = 304 nm, Em = NA), acetonitrile (Ex = 255 nm, Em = 485 nm), and phosphate buffer saline (Ex = 240 nm, Em = 525) at room temperature. The findings suggest that highly polar aprotic solvents (such as DMF) induce structural dissociation into solvated molecular complexes, whereas DH-LFP has achieved optimal emission stability in phosphate-buffered saline (PBS) in comparison to acetonitrile, chloroform, hexane, and toluene when it is at room temperature. Rather than acting as a sensor, CsCu 2 Cl 2 I exhibits pronounced solvatochromism, which gives distinct solvent dependent optical responses associated with the asymmetrical coordination environment of the mixed halides. Furthermore, it is robust and highly stable over a wide range of temperatures.