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Knowledge of the mechanisms that take place at the selective contacts, located at the charge-transport-layer (CTL)/perovskite heterojunctions, is crucial for the optimization of perovskite solar cells. Anomalous high values of the low-frequency capacitance at open-circuit and short-circuit indicate a high accumulation of charge at the interfaces, which could hinder the extraction of charge and increase hysteresis in current–voltage curve. To investigate this issue, we develop a simulation model based on the drift-diffusion differential equations with specific boundary conditions at the interfaces. We have simulated the CTL/perovskite structures as part of the entire perovskite solar cell, in order to establish the realistic energy profile across the interfaces. The energy profile allows to detect in which situations free charge accumulation at the interfaces exists, and to quantify this accumulation as a function of the device and …