Construction of ZnO/ZnS/CdS/CuInS₂Core–Shell Nanowire Arrays via Ion Exchange: p–n Junction Photoanode with Enhanced Photoelectrochemical Activity under Visible Light

Abstract

ZnO/ZnS/CdS/CuInS2 core-shell nanowire arrays with enhanced photoelectrochemical activity under visible light were successfully prepared via ion exchange and hydrothermal methods. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis absorption, X-ray photoemission spectroscopy, and photoelectrochemical response. As a p-n junction photoanode, ZnO/ZnS/CdS/CuInS2 heterostructure shows much higher visible light photoelectrocatalytic activity toward water splitting than ZnO/ZnS/CdS and ZnO/ZnS films. The ZnO/ZnS/CdS/CuInS2 film with optimal constitution exhibits the highest photocurrent of 10.5 mA/cm(2) and the highest IPCE of approximately 57.7% at 480 nm and a bias potential of 0 V versus Ag/AgCl. The critical roles of CdS and ZnS in ZnO/ZnS/CdS/CuInS2 heterostructure were investigated. ZnS, as a passivation layer, suppresses the recombination of the photogenerated charge carriers at the interface of the oxide and CuInS2. CdS enhances the absorption of visible light and forms p-n junctions with CuInS2, which promotes the transport of charge carriers and retards the recombination of electrons and holes in CuInS2 to improve the photoelectrochemical performance of ZnO/ZnS/CdS/CuInS2 heterostructure.

The phase transformation of CuInS2 from chalcopyrite to wurtzite

“…Compared with chalcopyrite CuInS 2 , the wurtzite CuInS 2 showed a higher and broader absorption in the entire visible region and near-infrared region. The bandgap can be determined by plotting (αhν) 2 versus hν (α = absorbance, h = Planck's constant, and ν = frequency) [26,27]. As shown in the inset picture, the calculated optical bandgap for chalcopyrite and wurtzite CuInS 2 is about 1.54 and 1.47 eV, respectively, which is close to the bulk energy bandgap of CuInS 2 .…”

“…In the previous studies, CuInS 2 has been found to exist in three different crystal structures: chalcopyrite, zinc blende, and wurtzite [4][5][6]. Chalcopyrite CuInS 2 is the most common existing phase at room temperature, whereas those with zinc blende and wurtzite structures are stable only at high temperatures.…”

“…As an I-III-VI 2 ternary semiconductor compound with a direct bandgap of 1.5 eV at room temperature, CuInS 2 is a promising material for photovoltaic applications because of its low toxicity, high absorption coefficient, and high theoretical photovoltaic conversion efficiency (about 25% to 30%) [1][2][3].…”

Facile Conversion Synthesis of Densely-Formed Branched ZnO-Nanowire Arrays for Quantum-Dot-Sensitized Solar Cells

“…For the ZnO/ZnO nanowire/nanoparticle formation, the HRTEM images (Fig. 3(c)) exhibit many ZnO nanoparticles on the surface of the nanowires (with the lattice spacing of 0.26 and 0.28 nm, respectively, for the ZnO (002) and (100) planes [32,33]). Then, after the hydrothermal process, hierarchically branched ZnO nanowire arrays are successfully synthesized (Fig.…”

Preparation and Photoelectrochemical Properties of CdS Nanoparticles Using Supercritical Carbon Dioxide

“…[1][2][3][4][5][6] The oxygen evolution reaction (OER) is the key to renewable-energy technologies, such as rechargeable metal-air batteries and water splitting. Water oxidation has an important function in the storage of energy, such as in solar fuel synthesis.…”