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

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 mu m) 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 mu m-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.