Compact Model and Detailed Balance Limit for a Dual n‐Type Direct Z‐Scheme Heterojunction

This paper presents a comprehensive study on a compact model and the detailed balance limit for a dual n‐type direct Z‐scheme heterojunction. The compact model developed in this work describes the current–voltage (IV) characteristics of the staggered heterojunction under one‐sided illumination. The model incorporates charge neutrality, surface recombination, thermionic emission over the barrier, and surface potentials. By considering these factors, the IV curve of the staggered heterojunction is captured, shedding light on the charge transfer and separation processes within the device. The heterojunction device consists of two photosystems: photosystem one (PSI) with a wide band gap and photosystem two (PSII) with a narrow band gap. Furthermore, the paper establishes the detailed balance limit for the efficiency of the dual n‐type direct Z‐scheme heterojunction. The maximum achievable efficiency, estimated to be 11.4%, is determined by the interplay between the band gap of PSII and the empirical relation for the maximum barrier for electrons leaving PSII. This detailed balance limit represents the highest efficiency that can be attained, accounting for carrier generation, recombination, and charge transfer mechanisms. The compact model and the derived detailed balance limit provide insights for designing and improving the performance of direct Z‐scheme heterojunctions. This paper presents a study on a dual n‐type direct Z‐scheme heterojunction, emphasizing its compact model and detailed balance limit. Analyzing current–voltage characteristics, it integrates fundamental principles‐charge neutrality, surface recombination, thermionic emission, and surface potentials. The established detailed balance limit, at 11.4%, hinges on the interplay between PSII bandgap and the maximum barrier for electron departure. The insights aid in advancing direct Z‐scheme heterojunctions for efficient solar energy conversion in artificial photosynthesis and renewable energy applications.