Reversible switching between quinoid and benzoid structures in PEDOT:PSS layer on CdS/CdSe photoanode for promoting photoelectrochemical performance

Abstract

Environmental problems have made the development of sustainable energy technologies such as photoelectrochemical (PEC) cells essential. In this study, a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS, PP) conductive polymer is successfully introduced onto a CdS/CdSe heterostructure, and an organic-inorganic hybrid CdS/CdSe/PP photoanode is fabricated using facile hydrothermal, chemical bath deposition, and spin coating methods. The PP polymer is a well-known conductive polymer with excellent hole transports, and it can enhance the PEC performance of a CdS/CdSe photoanode by infiltrating the heterostructure. Furthermore, PP improves the surface oxidation reaction with a hole scavenger by switching between quinoid and benzoid forms. The resulting CdS/CdSe/PP photoanode exhibits a significantly higher photocurrent density (21.8 mA cm⁻²) compared to CdS/CdSe (2.46 mA cm⁻²) and CdSe/PP (8.35 mA cm⁻²) photoanodes. During the fabrication of the photoanode, the CdS layer plays a crucial role in changing the final CdSe morphology from a cauliflower-like structure to a plate-like structure, which also affects the PP layer deposition characteristics. These findings highlight a new possibility for enhancing the PEC performance of photoanodes using a PP layer and a hole scavenger, and they also demonstrate the feasibility of manipulating the surface morphology of a CdS preformed layer.