Bandgap Engineering and Enhancing Optoelectronic Performance of a Lead-Free Double Perovskite Cs2AgBiBr6 Solar Cell via Al Doping

In this study, solar cells based on pure Cs2AgBiBr6 and Al-doped metal were fabricated using the sol-gel spin-coating technique. X-ray diffraction (XRD) analysis confirmed the formation of cubic-structured films for both pure and Al-doped. Notably, the grain size of Al-doped Cs2AgBiBr6 was observed to be larger than that of its pure counterpart. The optical properties of these films were investigated using UV-vis spectroscopy, revealing essential parameters such as the bandgap energy (E-g), refractive index (n), extinction coefficients (k), and dielectric constant. While the pure film exhibited an E-g of 1.91 eV, the Al-doped film demonstrated a slightly lower E-g of 1.82 eV. Utilization of these films in solar cell fabrication yielded intriguing results. The J-V curve shows that the pure solar cell displayed a short-circuit current density (J(sc)) of 5.01 mA/cm(2), a fill factor (FF) of 0.67, an open-circuit voltage (V-oc) of 0.89 V, and an efficiency of 3.02%. Al doping led to improvements, with an increase in V-oc to 0.91 V, FF to 0.71, and J(sc) to 5.29 mA/cm(2). Consequently, the overall efficiency surged to 3.40%, marking a substantial 12.5% enhancement compared with the pure solar cell. These findings underscore the efficacy of Al doping in enhancing the performance of Cs2AgBiBr6-based solar cells.