This review comprehensively examines the role of Transparent Conductive Oxides (TCOs) in Photoelectrochemical (PEC) devices, highlighting their significance in converting solar energy. TCOs, such as zinc oxide (ZnO), aluminum-doped zinc oxide (AZO), indium oxide (In2O3), tin-doped indium oxide (ITO), and fluorine-doped tin oxide (FTO), are crucial for enhancing the efficiency and effectiveness of PEC devices. The review discusses the properties, fabrication techniques, and challenges associated with TCO materials, emphasizing the importance of transparency, conductivity, and chemical stability. Key findings include: - Doping can improve TCOs' electrical conductivity while minimizing optical transmission loss. - Advanced modification techniques, such as element doping, plasma treatment, hot isostatic pressing, and carbon nanotube (CNT) modification, enhance surface energy, reduce particles and defects, and improve electrical conductivity. The implications of these findings suggest that TCO materials have significant potential for advancing photoelectrochemical conversion technology. Future research should focus on enhancing transparency and conductivity, developing advanced theories to understand structure-property relationships, and integrating multiple modification strategies to further improve TCO materials' performance in PEC devices.This review comprehensively examines the role of Transparent Conductive Oxides (TCOs) in Photoelectrochemical (PEC) devices, highlighting their significance in converting solar energy. TCOs, such as zinc oxide (ZnO), aluminum-doped zinc oxide (AZO), indium oxide (In2O3), tin-doped indium oxide (ITO), and fluorine-doped tin oxide (FTO), are crucial for enhancing the efficiency and effectiveness of PEC devices. The review discusses the properties, fabrication techniques, and challenges associated with TCO materials, emphasizing the importance of transparency, conductivity, and chemical stability. Key findings include: - Doping can improve TCOs' electrical conductivity while minimizing optical transmission loss. - Advanced modification techniques, such as element doping, plasma treatment, hot isostatic pressing, and carbon nanotube (CNT) modification, enhance surface energy, reduce particles and defects, and improve electrical conductivity. The implications of these findings suggest that TCO materials have significant potential for advancing photoelectrochemical conversion technology. Future research should focus on enhancing transparency and conductivity, developing advanced theories to understand structure-property relationships, and integrating multiple modification strategies to further improve TCO materials' performance in PEC devices.