Selective growth and photoelectrochemical properties of Bi2S3 thin films on functionalized self-assembled monolayers

Abstract

A convenient method for preparing highly crystalline Bi₂S₃ thin films by combining chemical bath deposition with self-assembled monolayers (SAMs) is described. The surface morphology, structure and composition of the resultant Bi₂S₃ thin films were characterized by XPS, XRD and FESEM, respectively. The optical and photoelectrochemical properties of as-prepared Bi₂S₃ thin films with different reaction times were investigated by UV-vis absorption and photocurrent action spectroscopy. It was demonstrated that these properties were dependent on the film thickness which increased with the deposition time. According to the different deposition mechanisms on the NH₂ and CH₃ terminal groups, patterned Bi₂S₃ microarrays with different feature sizes (50, 130, 250 μm) were successfully deposited on –NH₂-terminated SAMs regions of –NH₂/–CH₃ patterned SAMs surfaces. Clearly, with a decrease in feature size, the absorption intensity and photocurrent density of the patterned Bi₂S₃ thin film increased, which was due to the increased Bi₂S₃ surface area as well as the increased optical path length within the patterned Bi₂S₃ thin film, resulting from multiple reflection of incident light. The photocurrent density of the patterned thin film for the 50 μm-size feature exhibited an almost 9 times larger photocurrent density than a similar thin film without patterning. This work indicates that patterned Bi₂S₃ thin films are attractive systems for surface tailoring and also provide a novel approach to effectively control the photoelectrochemical properties of nanostructured Bi₂S₃ thin films with promising applications in microsystem devices for solar energy conversion.