Numerical modeling of capacitance signatures of perovskite solar cells

Perovskite solar cells (PSCs) have drawn attention owing to their high-power conversion efficiency (PCE) and low manufacturing cost. Notable efforts have been made to further improve solar cells performance. However, an accurate assessment and resolving the issues responsible for the power conversion efficiency loss is required for future progress. Capacitance-based techniques such as capacitance-voltage (C-V) measurements are widely used to characterize the depletion region properties of PSCs, such as doping density and their distribution, built-in potential, and depletion region width can be extracted. Here, we present numerical simulation using the one-dimensional (1D) solar cell capacitance simulator (SCAPS) software to show that several factors must be taken into consideration in order to appropriately estimate the depletion region properties using C-V measurements. We find that the capacitance due to charge injection from the charge transport layers (CTLs) and charge accumulation at interfaces may significantly contribute to the measured capacitance of PSCs. We show that these contributions are very pronounced when the carrier density is low and the perovskite layer is thin. The low mobility and poor conductivity of CTLs may lead to voltage drop and the formation of built-in potential inside the CTLs. Accordingly, a measured built-in potential may represent the summation of voltage drop over the serially connected CTLs and perovskite layers. Our results provide important guidance for the suitable estimation of depletion region properties of PCSs using C-V measurements.