Investigation of bandgap grading on performances of perovskite solar cell using SCAPS-1D and impedance spectroscopy

•Using impedance spectroscopy as a new technique to optimize the different parameters of solar cells.•Optimization of bandgap of solar cell using dc-current.•Importance of the equivalent circuit to deduce the relaxation time of the cell.•Valorization of perovskite in the solar cell.•Correlation between impedance spectroscopy conventional methods. The optimization the bandgap of a solar cell is an important consideration to achieve better high efficiency. The ideal bandgap for a solar cell would be one that matches the energy of photons in the solar spectrum, allowing for the efficient absorption of light and conversion into electricity.In the current study; the performance of the perovskite-based solar cells was investigated numerically in band gap from 1.55 to 1.67 (eV) using the one-dimensional SCAPS simulation software not only for the current-voltage characteristics but also for the complex impedance (Z*). The effects of band gap energy of the perovskite absorber layer were evaluated from the J-V curves have shown a maximum efficiency is achieved at 1.61 (eV).From the analysis of the complex impedance (Z*) data only one maximum was observed in the Nyquist and Bode plots. In this case; further analysis war carried to explorethe complex modulus (M*) spectra. Therefore this analysis revealed the existence of tow clears maxima in the Nyquist and Bode plots. The de-convolution approach allowed us to identify the origin of each relaxation. In addition the electrical parameters such as the relaxation time (τ1), and the (τ2) related to the electron recombination and ionic transport were extracted. Moreover, a good correlation was obtained between all parameters from the I-V and complex modulus (M*) data to explain the maximum efficiency achieved at 1.61 (eV).These studies basically the combinationof the complex impedance (Z*) and modulus (M*) provide an appropriate path for the optimization of the solar cell efficiency.