Exploring the Capacitance–Voltage Response of Metal Halide Perovskite Solar Cells |
Rasha Awni A.1, 2, Zhaoning Song2, Abdul Quader2, Jared D. Friedl2, Adam B. Phillips2, Randay Ellingson2, Michael Heben2, Yanfa Yan2 1Department of Energy Engineering, College of Engineering, University of Baghdad,, Baghdad, --, Iraq /2Department of Physics and Astronomy, and The Wright Center for Photovoltaics Innovation and Commercialization (PVIC), University of Toledo, Toledo, OH, United States |
Capacitance-based techniques such as capacitance–voltage (C–V) measurements are widely used to study electrical properties such as the depletion region width, doping density distribution, and built-in potential for thin film solar cells. However, C–V curves and the corresponding Mott-Schottky (M–S) plots for emerging devices such as perovskite solar cells (PSCs) are not fully understood. This is mainly due to the measured M–S plots for PSCs showing a strong deviation from linearity that creates a curve of two or three regions. Here, we use one-dimensional (1D) solar cell capacitance simulator (SCAPS) software to simulate the capacitance response of PSCs to applied AC and DC voltages. We show that several charges contribute to the measured capacitance and create a distinctive region in the M–S plot. For a sufficiently doped perovskite layer, the M-S plot is linearly shaped. For an intrinsic perovskite layer, free carriers significantly contribute to the capacitance, which results in a two-region M-S plot. We find that the charge injection and accumulation at the interface regions of the perovskite layer and charge transport layers (CTLs) may significantly contribute to the measured capacitance of PSCs. We show that charge injection from the CTLs to perovskite layer is limited when the doping density of the CTLs is as high as 1×1019 cm-3. While charge injection is more pronounced when the doping density is lower than 1×1017 cm-3. A depletion region can be created inside both the CTL and perovskite layer. Three-region M-S plot can be formed due to charge accumulation at the interfaces. Our results provide important guidance for understanding the results of C–V measurements for PSCs. |