Impedance spectroscopy in perovskite materials: From fundamentals to applications

Perovskite materials have emerged as a versatile class of compounds with broad applicability in energy conversion, storage, sensing, and electronic devices, owing to their rich structural flexibility and diverse transport properties. Impedance spectroscopy (IS) has become an indispensable tool for probing the complex electrical behaviour of these materials, enabling the disentanglement of bulk, grain boundary, and electrode-related processes across a wide frequency range. This review provides a comprehensive overview of impedance spectroscopy as applied to perovskite systems, beginning with the fundamental principles of IS and equivalent circuit modelling, followed by an in-depth discussion of relaxation phenomena, defect chemistry, and charge transport mechanisms. Particular emphasis is placed on recent advances in understanding mixed ionic-electronic conduction, dielectric behaviour, and electrochemical interfaces in both inorganic and hybrid organic–inorganic perovskites. The review explores key applications including solid-state batteries, fuel cells, sensors, and photovoltaic devices, highlighting how impedance analysis informs material design and device optimization. The fundamental aspects of impedance spectroscopy, the key measurement techniques, and the interpretation of results are discussed. Furthermore, the review highlights recent advancements in using IS to optimize the fabrication processes and enhance the long-term stability of perovskite devices. Finally, challenges and emerging trends in operando IS, multi-dimensional analysis, and data-driven modelling are discussed, outlining future directions for the field. This work aims to bridge fundamental insights with practical implementation, providing a valuable resource for researchers engaged in the development and application of perovskite-based technologies.