Investigation of ultra-wide bandgap chloro‑perovskite materials for blue LED applications: Crystal structure, optical and DFT studies

A novel ultra-wide bandgap (UWBG) hybrid organic−inorganic perovskite (HOIP) compound, l-prolinium l-proline trichlorocadmate (II) {L-C₅H₉NO₂)(L-C₅H₁₀NO₂)CdCl₃}_n, has been synthesized and extensively characterized using various techniques including Single-crystal X-ray diffraction(SXRD), thermal analysis differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), spectroscopy methods (Infrared, Raman, Ultraviolet), and density functional theory (DFT). X-ray diffraction reveals that the CdCl₆polyhedra share faces through three coordinated chlorine atoms, forming infinite one-dimensional chains of [CdCl₃]_n running along the b-axis. The stability of this polymeric structure is maintained by 68.8 % of (N, O)–H···Cl(O) hydrogen bonds and 31.2 % of (CH···(O, Cl)) Van der Waals interactions. According to the IUPAC-IUB Biochemical Nomenclature, the protonated (L–ProH⁺) cation adopts configuration type A, while the disordered (L–Pro^±) zwitterions exhibit two configurations, types A and B. This compound demonstrates semiconducting properties, emitting bright blue light upon 360 nm ultraviolet excitation, with a direct band gap of 4.362 eV. The CIE chromaticity coordinates for {(L–ProH⁺)(L–Pro^±)CdCl₃}_n are x = 0,2478 et y = 0,2734and it shows a color rendering index (CRI) of 89 and a low correlated color temperature (CCT) of 17,751 K. Electronic transitions between the valence band (VB) and the conduction band (CB) occur through chloride Cl(3p) anions, {(L–ProH⁺)(L–Pro^±) entities [H(1 s), C(2p), O(2p)]}, chloride Cl(4p) anions, and Cd (5 s) cations.