Preparation and characterizations of visible light-responsive (Ag–In–Zn)S thin-film electrode by chemical bath deposition

Influences of Silver and Zinc Contents in the Stannite Ag2ZnSnS4 Photoelectrodes on Their Photoelectrochemical Performances in the Saltwater Solution

Multicomponent metal sulfide (stannite Ag₂ZnSnS₄) samples were grown onto the conductive metal oxide-coated glass substrates by using the sulfurization of cosputtering silver-zinc-tin precursors. Several [Ag]/[Zn + Sn] and [Zn]/[Sn] ratios were set in the metal precursors to investigate their influences on the crystal phases, microstructures, and physical properties of the stannite Ag₂ZnSnS₄ samples. The results of the crystal phases and the compositions of the samples showed that the stannite Ag₂ZnSnS₄ phase can be obtained using the two-step sulfurization process, which maintained the silver-zinc-tin precursors at 160 °C for 1 h and then kept them at 450 °C for 30 min under a sulfur/nitrogen atmosphere. N-type stannite Ag₂ZnSnS₄ samples with the carrier concentrations of 5.54 × 10¹² to 9.11 × 10¹² cm^-3 can be obtained. High resistivities of Ag₂ZnSnS₄ samples were observed because of the low values of carrier concentration. Increasing the silver content in the sample can improve its photoelectrochemical (PEC) performance because of the decrease in the sample resistivity. The ratio of [Ag]/[Zn + Sn] at 0.8 and the ratio of [Zn]/[Sn] set at 0.90 in the stannite Ag₂ZnSnS₄ sample had the highest PEC performance of 0.31 mA·cm^-2, with the potential set at 1.23 V versus the relative hydrogen electrode applied on the sample because of it having the lowest charge-transfer resistance in the electrolyte.

Electrochemical properties of an AgInS2 photoanode prepared using ultrasonic-assisted chemical bath deposition

Electrochemical impedance analysis revealed the hole-transfer step taking place directly from the valence band of AgInS₂ photoanode to the electrolyte.

Surface-engineered growth of AgIn₅S₈ crystals

The growth of semiconductor crystals and thin films plays an essential role in industry and academic research. Considering the environmental damage caused by energy consumption during their fabrication, a simpler and cheaper method is desired. In fact, preparing semiconductor materials at lower temperatures using solution chemistry has potential in this research field. We found that solution chemistry, the physical and chemical properties of the substrate surface, and the phase diagram of the multicomponent compound semiconductor have a decisive influence on the crystal structure of the material. In this study, we used self-assembled monolayers (SAMs) to modify the silicon/glass substrate surface and effectively control the density of the functional groups and surface energy of the substrates. We first employed various solutions to grow octadecyltrichlorosilane (OTS), 3-mercaptopropyl-trimethoxysilane (MPS), and mixed OTS-MPS SAMs. The surface energy can be adjusted between 24.9 and 50.8 erg/cm(2). Using metal sulfide precursors in appropriate concentrations, AgIn5S8 crystals can be grown on the modified substrates without any post-thermal treatment. We can easily adjust the nucleation in order to vary the density of AgIn5S8 crystals. Our current process can achieve AgIn5S8 crystals of a maximum of 1 μm in diameter and a minimum crystal density of approximately 0.038/μm(2). One proof-of-concept experiment demonstrated that the material prepared from this low temperature process showed positive photocatalytic activity. This method for growing crystals can be applied to the green fabrication of optoelectronic materials.

Synthesis and characterization of highly stoichiometric AgInSe2thin filmsviaa sol–gel spin-coating technique

Highly stoichiometric AgInSe2thin films have been prepared on a p-type Si(111) substrate by a sol–gel spin-coating technique. These films were annealed at different temperatures. The as-prepared and annealed films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and X-ray photoelectron spectroscopy (XPS). The XRD spectra showed that the crystal structure of the AgInSe2film was that of cubic fluorite chalcopyrite with lattice constantsa= 6.102 Å andc= 11.69 Å. The SEM images depicted the surface morphology as smooth and the spherical particles as uniformly distributed. The average particle size was increased as the annealing temperature increased. Using HRTEM images and SAED patterns for the as-synthesized and annealed thin films, the AgInSe2film was indexed to a pure polycrystalline chalcopyrite AgInSe2structure with a lattice spacing of around 0.3 nm. XPS spectra showed that the as-deposited AgInSe2film was Ag rich, while the AgInSe2films annealed at 523 and 623 K were In rich.