Synthesis and Optical Properties of Potassium‐Based Wide‐Bandgap Mixed–Halide Perovskite KPbF₂Cl Nanorods

ABX₃ halide–perovskites (HPs) have emerged as promising alternatives for optoelectronic devices owing to their excellent properties and low cost. Generally, A is either Cs or an organic molecule while B is Pb, or Sn and X = I, Br, or Cl. Here, ab initio calculations on K‐based new HP with X as a mixture of F and Cl are performed. Solid‐state synthesis leads to a mixed‐KPbF₂Cl HP with an orthorhombic structure as determined from X‐ray diffraction and energy‐dispersive X‐ray spectroscopy. The high formation energy (−0.546 eV atom⁻¹) shows excellent stability of this HP. Scanning electron microscopy reveals rodlike structures while X‐ray photoelectron spectroscopy is performed for chemical analysis. Diffuse reflectance shows it to have a wide bandgap of ≈4 eV, in good agreement with the band‐structure calculations. Further, a strong photoluminescence peak is found at ≈340 nm for radiative recombination of free excitons along with a broad emission peaking at ≈450 nm owing to the involvement of self‐trapped excitons associated with lattice distortion. The finding of this stable HP can lead to high‐frequency applications, along with other applications such as transparent and low‐loss optical windows, prisms, etc., as well as development of novel optical materials by doping.