Synthesis and characterization of Bi2S3 quantum dot-sensitized TiO2 nanorod arrays coated with ZnSe passivation layers

Stable Bi2S3 quantum dots (QDs) prepared by a modified successive ionic layer adsorption and reaction (SILAR) method were used to decorate TiO2 nanorod (TNR) arrays and enhance their photoelectrochemical (PEC) performance. In the above procedure, elemental sulfur vapor was utilized as a precursor instead of aqueous Na2S to prevent the photodecomposition of QDs, whereas the hydrolysis of the Bi precursor (Bi(NO3)3) was prevented by using 3-mercaptopropionic acid as a stabilizer, and interfacial charge recombination was inhibited by depositing ZnSe passivation layers. The prepared photoelectrodes were subjected to morphological, structural, compositional, and optical/PEC property analyses, and the ideal bandgap and high absorption coefficient of Bi2S3 QDs was shown to result in enhanced visible light absorption properties and PEC performance of QD-sensitized TNR thin films, as compared to those of bare TNR films. The deposition of ZnSe on sensitized films resulted in further PEC performance enhancement, achieving a photocurrent density of 0.11 mA/cm2 and an electron lifetime of 37.9 ms, which was attributed to the effective suppression of charge carrier recombination by ZnSe passivation layers. Thus, the facile synthesis and environmentally friendly nature of Bi2S3 QD-sensitized TNR films coated with ZnSe passivation layers make them promising components of solar energy-driven devices.