Consistent Interpretation of Time- and Frequency-Domain Traces of Ion Migration in Perovskite Semiconductors.

The migration of mobile ions through the metal halide perovskite layer is still one of the main reasons for the poor stability of perovskite solar cells, LEDs, and photodetectors. To characterize mobile ions in the perovskite layer, time- and frequency-based electrical measurements are promising techniques. However, the presence of transport layers complicates their interpretation, limiting the information about mobile ions that can be extracted, and it is not clear how different features in frequency- and time-domain measurements relate to mobile ions. Here, we characterize a transport-layer-free device with capacitance frequency, capacitance transient, and current transient measurements in the dark, under illumination, and at different temperatures. We extract characteristic ionic signatures from the measurements, which we reproduce with drift-diffusion simulations for each technique. This allows us to explain the origins of the different ionic signatures, advancing our understanding of how electronic characterization techniques can be used to study the properties of mobile ions.