Correlating hysteresis phenomena with interfacial charge accumulation in perovskite solar cells

The property of charge extraction at the contact between the perovskite and electron selective layer (ESL) is vital to the photovoltaic performance of perovskite solar cells (PSCs). The J-V hysteresis phenomenon is frequently observed when the PSC is limited by inefficient charge transfer across the perovskite/ESL interface. Drift-diffusion simulations are performed so as to correlate the hysteresis with the quality of the perovskite/ESL junction. A generalized charge exchange model is introduced into drift-diffusion equations for describing the dynamics of charge extraction at the perovskite/ESL contact. Our simulations demonstrate that inefficient charge extraction is one of the causes of j-V hysteresis. This is because limited charge transfer gives rise to a depletion domain in the ESL, and hence promotes the interfacial accumulation of charge carriers as well as movable ions. Furthermore, it is found that the incorporation of surface recombination into drift-diffusion simulations enables the loss in open circuit voltage to be simulated in PSCs with different charge transfer properties. The simulation results indicate that j-V hysteresis can be suppressed by improving the charge extraction property and suppressing surface recombination.