Bright future by controlling /8 phase junction of formamidinium lead iodide doped by imidazolium for solar cells: Insight from experimental, DFT calculations and SCAPS simulation

In this study, we investigated the potential of Formamidinium lead iodide (FAPbI3) thin films as an absorber layer in perovskite-based solar cells, due to their good optoelectronic properties. Specifically, we investigated the effects of doping FAPbI3 with imidazolium (IM) at various percentages (ranging from 0% to 8%) on the stability and phase of the material at the a/8 phase junction. To do this, we used a range of analytical techniques, including x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), and UV-visible spectroscopy. Our findings showed that 6% IM-doped FAPbI3 led to homogeneous perovskite films with a stable a-phase perovskite, large grain size, and no holes. We confirmed these results via Density Functional Theory (DFT) studies. Additionally, we analyzed the impact of 6% IM-doped FAPbI3 in the context of solar cell applications using SCAPS simulations. We introduced a stacked layer-based perovskite structure (FTO/TiO2/FAPbI3/MAPbI3/Spiro -MeoTAD/Au) and found that the device had a high power conversion efficiency (PCE) of 26.10%, with a fill factor (FF) of 88%, open-circuit voltage (VOC) of 1.18 V, and short-circuit current density (JSC) of 25.18 mA/cm2.