Investigation of Photoluminescent Characteristics in Bismuth-Doped Cs<sub>3</sub>Mo<sub>2</sub>Cl<sub>9</sub> Halide Perovskite: Implications for Light Emission Mechanisms
Aadil Ahmad Bhat, Tuiba Mearaj, Aaliyah Farooq, Ali S. Alshomrany, Zulfqar Ali Sheikh, Zheng Zhang, Shilpi Upadhyay, Wengang Bi
Abstract
This study presents the successful synthesis of Bi 3+ doped Cs 3 Mo 2 Cl 9, a lead-free vacancy-ordered halide perovskite, via a solvothermal method, for optoelectronic applications. Structural analysis using X-ray diffraction (XRD) confirmed the crystalline nature of the synthesized material, exhibiting a hexagonal phase with space symmetry P 6 3 / mmc . Optical absorption studies indicate the activity of material in the UV region, with absorption at approximately 350 nm and a calculated bandgap energy value of ∼3.54 eV through wood and the Tauc equation for the 5% Bi 3+ doped Cs 3 Mo 2 Cl 9 vacancy-ordered halide perovskite. Photoluminescence excitation spectra (PLE) exhibited a broad band centered at ∼360 nm, consistent with the 1 S 0 → 3 P 1 (A band) transition for 5% Bi 3+ doped Cs 3 Mo 2 Cl 9 . Contrasting with no emission from the pristine material, PL analysis revealed consistent emissions at ∼447 nm upon Bi 3+ ion incorporation with the full width at half-maximum (fwhm) of ∼49 nm under various excitation wavelengths. The emission is attributed to the 3 P 1 → 1 S 0 transition for all Bi 3+ doped Cs 3 Mo 2 Cl 9 vacancy-ordered perovskite. Photoluminescence quantum yield (PLQY) demonstrated a pronounced dependence on Bi 3+ concentration, reaching a maximum of 8.5% at the optimal 5% doping level before decreasing to 6% at 10% due to concentration quenching, as explained by the Blasse equation. This highest PLQY at 5% doping signifies an optimal balance between defect passivation and suppression of nonradiative pathways. Critically, this material exhibits exceptional environmental stability retaining >95% of its initial photoluminescence intensity and structural integrity under ambient conditions for >90 days. These findings highlight the potential of Bi 3+ doped Cs 3 Mo 2 Cl 9 perovskite with an optimized doping level for diverse optoelectronic applications, suggesting avenues for further exploration in light-emitting diodes (LED) technology, photovoltaics, and sensor development.