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Recently, lead-free perovskite solar cell (PSC) heterostructure using CH3NH3SnI3 (MASnI3) absorber layer received significant attention due to their superior device performance. However, the effect of deep defect state on device performance is only little known about the MASnI3 absorber based PSC. In the present study, initially we optimized the power conversion efficiency of the device via the bandgap tuning and electron affinity variations in MASnI3 absorber layer using SCAPS-1D simulator. Thereafter, the capacitance-voltage (C-V), Mott-Shottkey (MS) (1/C2-V) and conductance-voltage (G-V) measurements are performed through simulation approach, which confirmed a solid sign of deep defects in the perovskite heterostructure device. In addition, temperature dependent capacitance-frequency (C-f) characteristics confirmed the clear expectancy of thermally-induced variations in capacitance (or dielectric constant) under illumination and dark, respectively. Further, supremacy of the space charge region in MASnI3 based PSC is confirmed from the voltage dependent semicircular nature of the Nyquist plots. Shrink in the semicircles of the Nyquist plots with the increase of the forward bias voltage also confirm the improvement of carriers under forward bias which increase the conductivity and therefore decrease the impedance.
Kumar et al. (Mon,) studied this question.