Internal near-infrared emission from eco-friendly all-inorganic bimetal halide

Near-infrared (NIR) emissive materials have shown great potential in night-vision, food detection, biomedical imaging and anti-counterfeit technologies. Massive efforts have been devoted to extending the optical performance of metal halides to the NIR region to expand their applications. Generally, NIR metal halides are mostly realized through lanthanide ions doping technique. However, doping usually leads to the formation of more defects, which will result in non-radiative recombination and low luminous efficiency. Based on this situation, a more efficient way is to find a single internal NIR emission material. In this paper, the lead free near-infrared emitted CsAgBr2 had been successfully synthesized by the antisolvent reprecipitation method. An NIR emission around 825 nm with large FWHM and Stokes shift was realized. The lifetime and bandgap of it were measured to be ∼2.78 μs and 3.74 eV, respectively. The broadband emission with large Stokes shift and long PL decay lifetime suggested that the PL origin might be attributed to self-trapped excitons. The exciton binding energy of CsAgBr2 was much higher than the thermal energy of room temperature, indicating that the NIR emission of it could stably exist at room temperature. This eco-friendly single NIR phosphor synthesized by convenient method will have prospect to promote the development of NIR spectroscopy technology.