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

In this study, solar cells based on pure CsAgBiBr 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 CsAgBiBr 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 (), refractive index (), extinction coefficients (), and dielectric constant. While the pure film exhibited an of 1.91 eV, the Al-doped film demonstrated a slightly lower of 1.82 eV. Utilization of these films in solar cell fabrication yielded intriguing results. The - curve shows that the pure solar cell displayed a short-circuit current density () of 5.01 mA/cm, a fill factor (FF) of 0.67, an open-circuit voltage () of 0.89 V, and an efficiency of 3.02%. Al doping led to improvements, with an increase in to 0.91 V, FF to 0.71, and to 5.29 mA/cm. 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 CsAgBiBr-based solar cells.