fig24

Figure 24. Schematic of band structure and charge carrier transfer of traditional heterojunction systems (A-C), a p-n heterojunction system (D)^[191], a direct Z-scheme heterojunction system (E)^[194], a step scheme heterojunction system (F)^[201], a Schottky junction system (G)^[204] and a surface heterojunction system (H)^[205].