Enhanced performance of V²⁺-doped MAPbI₂Br perovskite films in solar cells: structural, optical, and photovoltaic insights

Sol-gel dip-coating technique has adapted a thin film of CH₃NH₃PbI₂Br (MAPbI₂Br) on a glass FTO substrate. The structure of the film shown from the X-ray diffraction is cubic, and the appearance indicates that the film is significantly crystalline. The V²⁺ 5%-doped film demonstrated a significant geometric increase in the crystallite size to 34.52 nm, a sharp decrease in the bandgap energy to 1.79 eV, an elevation in the refractive index to 2.41, and a decrease in the extinction coefficient to 1.66. Additionally, this material’s conduction band edge complements the TiO₂ electron transport layer appropriately. On the other hand, we constructed solar cells using the FTO/TiO₂/MAPbI₂Br/spiro-OMeTAD/Au configuration. Doping the MAPbI₂Br film with 5% V²⁺ yielded the most remarkable results. It had a current density of 8.42 mA/cm², an open-circuit voltage of 1.04 V, a fill factor of 0.76, and an efficiency of 6.58%. However, the electrochemical impedance spectroscopy (EIS) results for the same cell show that the device with 5% V²⁺ doping has a lower recombination rate than solar cells. This work has demonstrated that the doping effect of V²⁺ in the MAPbI₂Br perovskite films, made of the 5% V-doped modification in the form of solar cells, improves performance and lays the groundwork for future advancements in provskite solar cells.