In Sun Cho

A tree-like nanoporous WO3 photoanode with enhanced charge transport efficiency for photoelectrochemical water oxidation

We report a tree-like nanoporous tungsten trioxide (WO3) photoanode that largely improves the photoelectrochemical water oxidation performance. These novel WO3 photoanodes were prepared using a pulsed laser deposition method and their porosity was controlled by adjusting the oxygen partial pressure during the deposition process. The tree-like nanoporous WO3 photoanode has a nanoporous structure with a partially preferred alignment of the individual WO3 nanocrystals, which greatly improves the charge transport efficiency. Under simulated solar light illumination, the aforementioned features resulted in ∼9 times higher photocurrent density (1.8 mA cm−2 at 1.23 V vs. RHE) than a dense WO3 photoanode. An incident photon-to-current conversion efficiency of over 70% was also obtained at wavelengths of 350–400 nm.

Boosting the solar water oxidation performance of a BiVO4 photoanode by crystallographic orientation control

Materials with low crystal symmetry often exhibit anisotropic properties, allowing the tuning of their physical and chemical properties via crystallographic orientation and exposed facet control. Herein, for the first time, we have demonstrated that pristine BiVO4 with a preferred [001] growth orientation and exposed (001) facets exhibits excellent intrinsic charge transport properties and surface reactivity. Using preferentially [001]-oriented BiVO4 (p-BVO) as a photoanode for photoelectrochemical water splitting, an impressive photocurrent density at 1.23 V vs. the reversible hydrogen electrode (RHE) is achieved, which is approximately 16 times higher than that exhibited by a photoanode based on randomly oriented BiVO4. Importantly, when the surface of p-BVO is further roughened and decorated with an oxygen evolution electrocatalyst, photocurrent densities of ∼3.5 and ∼6.1 mA cm−2 are achieved at 0.6 and 1.23 VRHE, respectively; the latter value corresponds to ∼82% of the theoretically achievable photocurrent density for BiVO4 under 1 sun illumination. Our results demonstrate the effectiveness of crystal orientation and exposed facet control in optimizing materials for solar water-splitting applications.

Plasmon-enhanced ZnO nanorod/Au NPs/Cu2O structure solar cells: Effects and limitations

Cu-based compounds can be a good candidate for a low cost solar cell material. In particular, CuxO (x : 1–2) has a good visible light absorbing bandgap at 1–2 eV. As for using nanostructures in solar cell applications, metal nanoparticle-induced localized plasmon resonance is a promising way to increase light absorbance, which can help improve the efficiency of solar cells. We fabricated ZnO nanorod/Au nanoparticles/Cu2O nanostructures to study their solar cell performance. ZnO nanorods and Cu2O layer were synthesized by the electrodeposition method. Size-controlled Au nanoparticles were deposited using E-beam evaporator for localized surface plasmon resonance (LSPR) effect. By inserting Au plasmon nanoparticles and annealing Au NPs in solar cells, we could tune the maximum incident photon-to-current efficiency wavelength. However, the potential well formed by Au NP at the ZnO/Cu2O junction leads to charge-trapping, based on the constructed electronic band analysis. LSPR-induced hot carrier generation is proposed to promote carrier transport further in the presence of Au NPs.

ZrO2 Nanoparticle Embedded Low Silver Lead Free Solder Alloy for Modern Electronic Devices

In this article, the authors present the synthesis of Sn–1.0Ag–0.5Cu (SAC105) alloy embedded with zirconium oxide nanoparticles using simple mechanical blending and casting route. The cast samples were characterized in terms of microstructural evolution, wetting, microhardness, and drop test reliability. The characterizations were performed by using a tabletop X-ray diffraction, field emission scanning electron microscope, and the compositions were identified by energy dispersive spectroscopy. The results showed that addition of ZrO2 nanoparticles significantly refines the grain size, Ag3Sn, and Cu6Sn5 intermetallic compounds thickness by 46, 14, and 26% respectively as compared to the single component SAC105 alloy. The results were also compared with those of standard Sn–3.0Ag–0.5Cu (SAC305) alloy. Although the spreading and microhardness of SAC105 is found to be slightly poor or comparable to SAC305 yet drop test reliability can be improved significantly after addition of ZrO2 nanoparticles appreciably. This kind of refinement results in a cheap alternative to SAC305 with comparable mechanical strength and high solder joint reliability.Graphical Abstract