Characterization of photoelectrochemical energy devices by electrochemical impedance analysis: a mini review

Abstract Electrochemical impedance spectroscopy (EIS) is a powerful non-destructive analytical technique that enables quantitative analysis of complex electrochemical processes occurring at electrode–electrolyte interfaces in electrochemical systems. This review introduces the fundamental principles of EIS analysis and equivalent circuit modeling, and systematically presents methodologies for their application to next-generation solar cells and photoelectrochemical (PEC) hydrogen production systems. In electrochemistry-based solar cells such as dye-sensitized solar cells (DSSCs) and quantum dot-sensitized solar cells (QDSCs), EIS enables the separate analysis of electron transport characteristics within photoelectrodes, charge recombination at interfaces, and counter electrode catalyst activity, providing key design parameters for improving photoconversion efficiency. Furthermore, in PEC cell-based hydrogen production systems, quantitative evaluation of charge transfer resistance, charge recombination characteristics, and mass transfer rates at semiconductor photoelectrodes allows for the derivation of performance optimization strategies for photoanodes and photocathodes. Through various research cases, this review demonstrates that EIS analysis is a valuable tool for simultaneously characterizing both thermodynamic and kinetic aspects of electrochemical solar cells and PEC hydrogen production devices, thereby providing practical directions for performance enhancement and commercialization of PEC energy conversion technologies.