Impedance Spectroscopy for Metal Halide Perovskite Single Crystals: Recent Advances, Challenges, and Solutions

Metal halide perovskite single crystals (MHPSCs) are gaining enormous attention in the energy research community due to their impressive responses both in optical sensing and in photovoltaics. The switching from polycrystalline to monocrystalline morphology, not only allows to maintain the outstanding properties that characterize perovskite materials, but also enhances them. However, the poor control over the thickness and size during growing methods leads to considerable differences between surface and bulk responses. Impedance spectroscopy (IS) has been revealed as a powerful technique to understand the kinetics governing polycrystalline perovskite materials. The ionic migration, trap states, and recombination mechanisms occurring in both bulk and surface of the MHPSCs, need to be analyzed in depth to exploit their full potential. Here, we highlight the importance of IS to further advance our knowledge about monocrystalline perovskite materials, bringing to the table the relevance of other small perturbation techniques to complement the IS.