Andriy V. Kozytskiy

Non-stoichiometric Cu–In–S@ZnS nanoparticles produced in aqueous solutions as light harvesters for liquid-junction photoelectrochemical solar cells

A direct “green” aqueous synthesis of mercapto acetate-stabilized copper indium sulfide (CIS) nanoparticles (NPs) and core/shell CIS@ZnS NPs of a varied composition under ambient conditions and a temperature lower than 100 °C is reported. The CIS@ZnS NPs can be anchored to the surface of nanocrystalline FTO/TiO2 films without additional purification or ligand exchange steps yielding visible-light-sensitive heterostructures ready for using as photoanodes in the liquid-junction solar cells. The highest photoelectrochemical activity in a three-electrode cell was demonstrated by a TiO2/CIS@ZnS heterostructure with atomic Cu : In : S and Zn : Cu ratios of 1 : 5 : 10 and 1 : 1. The optimized TiO2/CIS@ZnS photoanodes were tested in two-electrode solar cells with aqueous polysulfide electrolyte and TiO2/Cu2S heterostructures produced by a photo-assisted method as counter-electrodes. Under illumination by a 30 mW cm−2 xenon lamp, the optimized cells showed the average light conversion efficiency of 8.15%, the average open-circuit voltage of −0.6 V and the average fill factor of 0.42. The cells revealed excellent stability and reproducibility of photoelectrochemical parameters with around one percent variation of the light conversion efficiency around an average value for six identical solar cells.

Effect of the Method of Preparation of ZnO/CdS and TiO2/CdS Film Nanoheterostructures on Their Photoelectrochemical Properties

A study was carried out on the photoelectric properties of ITO/TiO2/CdS and ITO/ZnO/CdS nanostructurized films obtained by the SILAR method and the photocatalytic reduction of sulfur by ethanol in the presence of Cd(II) salts. The nanostructures obtained by the latter method display much higher photocurrent density (by a factor of 2 in the case of systems derived from ZnO and a factor of 5 in systems derived from TiO2) upon irradiation with white light (λ > 400 nm) in aqueous solutions of sodium sulfide than the heterostructures obtained by the traditional SILAR method.

Structured Films of CuxS – Counter Electrodes for Solar Cells Based on FTO/ZnO/CdS Heterostructures and Sulfide/Polysulfide Redox Couple

It was shown that nanostructured films of zinc oxide electrodeposited on the surface of conducting FTO glass can be converted into copper sulfide CuxS without affecting their morphology. The FTO/CuxS films can be used as electrocatalytically active cathodes in solar cells based on a FTO/ZnO/CdS photoanode sensitive to visible light and a sulfide/polysulfide redox couple. By using the FTO/CuxS films in place of platinum foil it is possible to increase the efficiency of light conversion by more than 20 times, from 0.07% to 1.4%.

Photoelectrochemical Solar Cells with Semiconductor Nanoparticles and Liquid Electrolytes: a Review

The principles for the function of solar cells made with semiconductors and liquid electrolytes and methods for the preparation of components for these cells are surveyed. Methods for enhancing the efficiency of light conversion by creating intermediate barrier layers in the photoanodes, band design of nanoscale semiconductor sensitizers, morphology of wide-bandgap oxide transport layers, as well as the composition and structure of counter electrodes were discussed. Special attention was given to an analysis of current trends in the development of such cells, including the use of low-toxicity and accessible semiconductor and carbon nanomaterials as well as new methods for the formation of nanostructured electrodes.

Photoelectrochemical Properties of Titanium Dioxide Nanoheterostructures with Low-Dimensional Cadmium Selenide Particles

Feasibility was demonstrated for the use of low-dimensional CdSe@CdS particles with core@shell structure and 1.8-2.0 nm mean core diameter as a component in the FTO/TiO2/CdSe@CdS photoanode in photoelectrochemical solar cells with aqueous polysulfide electrolyte and copper sulfide-based counter-electrode. An average light conversion efficiency of 6.3% was achieved (at excitation intensity of 30 mW/cm2) in cells with the FTO/TiO2/CdSe@CdS photoanode and an FTO/TiO2/Cu2S counter-electrode produced by sulfidation of copper particles photochemically deposited onto the titanium dioxide surface.

Photoelectrochemical Properties of Nanoheterostructures Based on Titanium Dioxide and Ag-In-S Quantum Dots Produced by Size-Selective Precipitation

The photoelectrochemical properties of FTO/TiO2/AIS nanoheterostructures containing Ag-In-S (AIS) nanoparticles (NPs) produced by the size-selective precipitation were investigated. It was found that the photocurrent of such composites increases by almost twice with decrease of the average AIS NP size from 3.5-4 to ~2 nm. The dependence of the rate constant of photoinduced electron transfer between AIS NPs and TiO2 on the average size of the NPs is similar in nature and agrees with the size dependence of the photoelectrochemical activity of TiO2/AIS nanoheterostructures.

Photovoltaic Characteristics of Bis(2-Benzimidazolyl)-Bisthiazole Deposited on TiO2 in the Presence of Zn2+Ions

It was found that bis(2-benzimidazolyl)bisthiazole deposited on nanosized TiO2 in the presence of Zn2+ salts was able to generate a photocurrent upon irradiation by visible light in a cell with a solution of KI in acetonitrile. The activity of this compound was probably caused by the presence of the benzimidazole fragment (electron donor) and the bisthiazole group (electron acceptor), while zinc(II) played a role of agent, required for formation of an insoluble coordination compound on the surface of the TiO2. From comparison of the results with published data it can be concluded that the open-circuit potential of photovoltaic cells containing a benzimidazole fragment decreases with decrease in the energy of lowest unoccupied molecular orbital.