Ramifications of co-substitution on crystal structure and optical performance of RT synthesized Cs1-xPbI3-x - xRbCl (x=0 to 0.8) solid solutions

Abstract

δ-CsPbI3, a stable yellow-colored and orthorhombic polymorph of CsPbI3, has been subjected to compositional engineering by incorporating stoichiometric amounts of RbCl via mechanochemical synthesis method. Such developed compositions Cs1-xPbI3-x-xRbCl that facilitates both cation/anion exchange, have been explored for their in-depth structural modification and optical properties. The bond distances were obtained through Rietveld refinement of the high-resolution X-ray diffraction data. The distortion index calculated for the Pb–I octahedra increased from 0.017 for x = 0 to 0.021 for x = 0.8 indicating stronger distortion in the lattice with RbCl incorporation. Absorption wavelength of the compositions shifted to lower wavelengths with increase in x. Resultantly, band gap calculated (Eg) also increased from 2.41 eV to 2.73 eV with increase in x – which affirms the narrowing of bands via small dopants. Photoluminescence studies carried out on the as-synthesized solid solutions showed single emission around 567 nm for x = 0

whereas two emission wavelengths observed around 515 nm and 577 nm (green region) for x = 0.2 to 0.8. Better PL intensities observed exclusively for the RbCl substituted compositions may be attributed to the defect-mediated suppression of non-radiative process. ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠ © 2025 Elsevier Ltd