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.