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

Abstract

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.

Ion Migration in Organic–Inorganic Hybrid Perovskite Solar Cells: Current Understanding and Perspectives

“…[102] In fact, this large capacitance that occurs in the low-frequency (LF) domain is also considered by other works as a way to detect the ion migration and the degree of accumulation at the interface. [103,104] IS works by monitoring the response of the sample to an electric field and as a function of frequency (ω). The complex impedance Z (Ω cm −2 ) is obtained from the relationship between the AC voltage and current response.…”

“…On the basis of the dominant role of ion migration at grain boundaries, it is crucial to suppress ion migration by passivating the defects at grain boundaries. [93][94][95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112] Liu et al proposed a strategy to passivate grain boundaries and inhibit ion migration by methimazole (MMI). [113] From the EDS results, it can be seen that the intensity of I in the initial aging device decreased from the HTL side to the ETL side, indicating that I migrated in the perovskite (Figure 9a).…”

“…On the basis of the dominant role of ion migration at grain boundaries, it is crucial to suppress ion migration by passivating the defects at grain boundaries. [ 93–112 ] Liu et al. proposed a strategy to passivate grain boundaries and inhibit ion migration by methimazole (MMI).…”

Coupling between Ion Drift and Kinetics of Electronic Current Transients in MAPbBr3 Single Crystals

“…The high-frequency resistance ( R ) values were normalized and shown to follow a trend R ∝ t 1/2 (see Figure S6 ), in agreement with the IDD model (see section S2 of the Supporting Information). 17 , 21 …”

“…The ion migration in MAPbBr 3 SCs has been investigated through different methods (see Table S1 in the Supporting Information ). 17 − 20 Several hypotheses have been suggested to distinguish ionic from electronic contributions to the measured current density ( J ) flowing through perovskite-based samples. 20 − 25 Nevertheless, there is no conclusive evidence nor consensus on the most appropriate model.…”