Influence of annealing temperature on microstructure and photoelectric properties of ternary CdSe@CdS@TiO2 core–shell heterojunctions

CdSe@CdS@TiO 2 microsheet array (MSA) ternary core–shell heterojunctions were prepared by successive electrodeposition of CdS and CdSe onto TiO 2 microsheets using cyclic voltammetry. The photoelectrochemical performance of CdSe@CdS@TiO 2 MSAs ternary core–shell heterojunctions is significantly improved. This structure not only greatly enhances the utilization efficiency of visible light but also greatly extends the spatial separation of photoinduced charge. This is because CdSe@CdS@TiO 2 MSAs ternary core–shell heterojunctions have an inherent cascade energy band structure and a high-quality contact between each other at the interface. After annealing, CdSe@CdS@TiO 2 MSAs ternary core–shell heterojunctions show a further improved photoelectrochemical performance because the formation of ternary compound CdS 1− x Se x enhances the quality of the contact interface between CdSe and CdS layers and consequently increases the transportation efficiency of photoinduced charges and injection efficiency of photoinduced electrons to the TiO 2 layer. The maximum photocurrent density of 3.5 mA/cm 2 was observed in the CdSe@CdS@TiO 2 MSAs ternary core–shell heterojunctions after annealing at 350 °C, which is 9.46, 3.18 and 2 times higher than that observed in CdS@TiO 2 MSA, CdSe@TiO 2 MSA, and as-prepared CdSe@CdS@TiO 2 MSA photoelectrodes, respectively.