Modification of Ag8SnS6 Photoanodes with Incorporation of Zn Ions for Photo-Driven Hydrogen Production

Abstract

In this study, Zn ions were incorporated into Ag8SnS6 thin films on glass and indium–tin–oxide-coated glass substrates using chemical bath deposition. Detailed procedures for the growth of Ag–Zn–Sn–S semiconductor films and their optical, physical and photoelectrochemical performances were investigated. X-ray diffraction patterns of samples revealed that kesterite Ag2ZnSnS4 phase with a certain amount of Ag8SnS6 phase can be obtained using ethylenediaminetetraacetic acid disodium salt and trisodium citrate as the chelating agent couples. Images of field-emission scanning electron microscope showed that plate-like microstructures with some spherical aggregates were observed for the sample at low Zn content. It changed to irregular spherical grains with the [Zn]/[Sn] ratios being higher than 0.95 in samples. The energy band gaps of the samples were in the range of 1.57–2.61 eV, depending on the [Zn]/[Sn] molar ratio in sample. From the Hall measurements, the carrier concentrations and mobilities of samples were in the ranges of 6.57 × 1012–1.76 × 1014 cm−3 and 7.14–39.22 cm2/V·s, respectively. All samples were n-type semiconductors. The maximum photoelectrochemical performance of sample was 1.38 mA/cm2 in aqueous 0.25 M K2SO3 and 0.35 M Na2S solutions.