Classification and Characterization Methods for Heterojunctions

Abstract Heterojunction constructions are usually used to promote the separation of photocarriers and improve the photocatalytic activities. However, misuse and confusion often occur in current research because there are no unified rules for the classification and naming of heterojunctions. In order to avoid this problem, this review summarizes and standardizes the classification and naming rules of heterojunctions, based on different band structure distribution of the two semiconductors in heterojunctions and transfer paths of photogenerated carriers. Moreover, the distinctions in photogenerated carrier behavior among O–scheme heterojunction, Z–scheme heterojunction, and S–scheme heterojunction within type II heterojunction are clearly elucidated. Additionally, current methodologies for identifying heterojunction types, including metal–ion photo–deposition, in situ X–ray photoelectron spectroscopy, surface photovoltage spectroscopy, transient absorption spectroscopy, and cathodoluminescence spectrometry, are summarized. This review also highlights the applicability of various heterojunction types across different photocatalytic applications and suggests future directions for heterojunction research.