One of the remaining issues, impeding the commercialization of the low cost and high efficiency perovskite solar cells (PSCs) is whether the halide perovskite materials have sufficient stability. Two important instabilities are the light-induced degradation1 and the scan-dependent performance, namely the hysteresis effect2. Using experimental parameters and parameters obtained from atomistic modelling, the perovskite/Au, perovskite/WOx and perovskite/PCBM interfaces are numerically investigated and compared to the experimental current-voltage (J-V) and capacitance-voltage (C-V) characteristics3. Besides interface states, the effect of mobile ions are taken into account in the drift-diffusion approach for more realistic modelling. As a result, the experimental build in potential (Vbi) variation, open circuit voltage (VOC) loss, hysteresis effects and photocurrent degradation/recovery can be explained. The interplay between interface traps and mobile ions is assumed to lead the anomalous hysteresis, while local trap states are considered as the main cause of performance degradation as a function of time. Furthermore, a new approach is proposed to the modelling of Kelvin Probe Force Microscopy (KPFM) of hetero-structures in dark and under illumination, aiming at estimating the surface states on the top of materials and understanding the carrier operation inside the cells. 1. Nie, W. et al. Light-activated photocurrent degradation and self-healing in perovskite solar cells. Nat. Commun. 7, 11574 (2016). 2. Snaith, H. J. et al. Anomalous Hysteresis in Perovskite Solar Cells. J. Phys. Chem. Lett. 5, 1511–1515 (2014). 3. Huang, Y. et al. Influence of Schottky contact on the C-V and J-V characteristics of HTM-free perovskite solar cells. EPJ Photovolt. 8, 85501 (2017).