Photoluminescence and lifetime studies of C-dot decorated CdS/ZnFe2O4 composite designed for photoelectrochemical applications

Abstract

Cadmium sulphide (CdS) is a well-known material for photoelectrochemical water splitting as a photoanode. The valence and conduction band edges are well suited for both hydrogen and oxygen evolution reactions. However, a major drawback in the case of cadmium sulphide is its photocorrosion. In this regard, formation of a Type II heterostructure helps in well separation of the photogenerated charge carriers and reduces photocorrosion. Herein, we have incorporated a carbon dot layer (high conductivity) in between a CdS/ZnFe2O4 Type II composite heterostructure to further enhance the photoelectrochemical performance of the material. Steady state photoluminescence (PL) study revealed that maximum PL intensity is observed in the case of bare CdS while minimum intensity in the case of ternary composite after the incorporation of carbon dots. The inflation of PL intensity revealed the overall increase in the conductivity and enhanced charge separation at the interface after composite formation. The time-resolved photoluminescence (TRPL) decay dynamics have also been studied. The lifetime of the charge carriers for the ternary composite was found to be 2.41 ns, which is much higher than the bare (0.78 ns) and binary composite (0.85 ns), indicating the improved charge separation and the stability after composite formation (CdS/C-dot/ZnFe2O4). This further aids in the enhancement of photocurrent generation. The photocurrent density is enhanced by approximately 50 times compared to the bare material (CdS) and 5 times compared to the binary composite (CdS/ZnFe2O4).