Deciphering hysteresis in perovskite solar cells: Insights from device simulations distinguishing shallow traps from mobile ions

abstract

In perovskite solar cells, a hysteresis of the current--voltage curve is often observed and is usually attributed to moving ions. However, our device modelling forecasts that it can also be explained, at least in part, by the occupation behaviour of slow-shallow trap states in the perovskite material. A difference between the ionic and trap interpretation arises in the illumination dependence of the hysteresis. Under the assumption of slow-shallow trap states, our simulations show that a diffusion capacitive effect should be observed at high scanning rates (\textgreater 100~V/s) and low light intensities (\textless 0.01 sun). This effect does not appear when assuming a device model with moving ion vacancies. This offers an opportunity for experimentally distinguishing between the two explanatory models and to quantify the relative contributions to hysteresis from ion vacancies and traps, respectively.