Meiling Sun

The enhanced photoelectrochemical performance of CdS quantum dots sensitized TiO2 nanotube/nanowire/nanoparticle arrays hybrid nanostructures

This study aims at improving the photoelectrochemical performance mainly from two aspects: the increased number of heterojunctions and the advantages of nanotube/nanowire/nanoparticle arrays hybrid nanostructures. TiO2 nanoparticles porous layer was sensitized by CdS quantum dots (QDs), and coated on the top of the material, hydrogen-treated TiO2 nanotubes with nanowires, which was also sensitized by CdS QDs (This nanostructure is defined as CdS/H:TTWP). CdS/H:TTWP was successfully fabricated by the methods of electrochemical anodization, successive ionic layer adsorption and reaction (SILAR) and sol–gel. The data from the photoelectrochemical (PEC) performance test shows that the photocurrent density of CdS/H:TTWP is 7.6 mA cm−2 at −0.43 V vs. Ag–AgCl under AM 1.5 G illuminations.

Embedded CdS nanorod arrays in PbS absorber layers: enhanced energy conversion efficiency in bulk heterojunction solar cells

Oriented and high-density n-type CdS nanorod arrays were successfully embedded in p-type PbS absorber layers by a facile and low-cost hydrothermal method and a chemical bath deposition method. The structural, optical and electrical properties of these samples were examined, and the results demonstrated that the high quality three-dimensional heterostructure was obtained. Further investigation revealed that the three-dimensional heterostructure possessed superior optical absorption property due to the optical scattering from the nanorod array. In addition, photovoltaic property measurements demonstrated that the energy conversion efficiency of the novel three-dimensional heterojunction solar cell was increasing by 35% in comparison with the standard planar heterojunction solar cell. The observed improvement is mostly attributed to the three-dimensional heterostructure enabling increased heterojunction area, improved charge carrier collection and enhanced optical absorption ability. This study demonstrates that the three-dimensional heterostructure has potential application in thin film solar cells, and the solution process represents a promising technique for large-scale fabrication of these novel solar cells.

Ag–Cu2O composite microstructures with tunable Ag contents: synthesis and surface-enhanced (resonance) Raman scattering (SE(R)RS) properties

Metal–semiconductor composite microstructures have recently been demonstrated to possess potential applications due to their unique structures. Ag–Cu2O composite microstructures (Ag–Cu2O CMSs) with tunable silver content have been synthesized with a facile in situ method. Ag contents on the surface of Cu2O can be tuned through the variation of the concentration of AgNO3, which further greatly affected the surface-enhanced (resonance) Raman scattering (SE(R)RS) performance. The Ag–Cu2O CMSs prepared with 0.4 mM AgNO3 show the optimum SE(R)RS properties, better than pure Ag NPs. Furthermore, the enhancement mechanism and uniformity of Ag–Cu2O CMSs are investigated in detail.

Synthesis of ZnO nanosheet array film with dominant {0001} facets and enhanced photoelectrochemical performance co-sensitized by CdS/CdSe

In this work, [110] oriented ZnO nanosheet (ZnONS) array films with a large percentage of high-energy {0001} surfaces were prepared for the first time with the assistance of sodium citrate. ZnONS array films possess prominent UV–visible absorption with an absorption edge at ~405 nm, indicating that the optical property of the semiconductor is dependent on a specific crystal structure and crystal plane. CdS and CdSe quantum dots (QDs) were assembled onto ZnONS array films to form a cascade structure of ZnONS/CdS/CdSe by the successive ionic layer adsorption and reaction method. The as-fabricated photoanode exhibits strong absorption in the visible spectrum up to 735 nm. With light illumination, the optimum photoanode yields a photocurrent of ~4.40 mA cm−2 at 0 V versus SCE, which is about 4.6 times of that of pure ZnONS samples. The excellent photoelectrochemical (PEC) properties of our photoanodes suggest that the QDs sensitized ZnONS array films with a large percentage of high-energy surfaces have potential applications in PEC solar cells.

Electrodeposition of a novel CdTe array on Ni foils and photoelectrochemical performance

A novel perpendicularly aligned CdTe array with cauliflower-like morphology was fabricated on a Ni substrate using a simple electrochemical synthesis method. The samples were characterized by XRD, EDX and FESEM, and the results demonstrate that a high-purity, uniform cauliflower-like CdTe array was obtained. Rod lengths can reach to 3.0 μm, with nanoparticles stacking along the rod growth direction, keeping the diameter at 1.5 μm. A schematic diagram of the possible growth process and evolution from CdTe seed nuclei to the cauliflower-like CdTe array was proposed. The device based on the aligned array-on-Ni configuration demonstrates excellent photoelectrical properties, which is ascribed to the large absorption coefficient of the material and also suggests good electronic structure quality of the cauliflower-like rods. The technique described is applicable to fabricate highly aligned cauliflower-like semiconductor arrays on other conductive substrates.

Effect of sintering temperature on the luminescence properties of Ca0.8Ba0.2TiO3:Pr3+ red-emitting phosphor

Nanoparticles with the nominal composition Ca0.8Ba0.2Ti03:Pr(3+) were prepared using the sol-gel process. Barium nitrate, 4-hydrated calcium nitrate and praseodymium oxide were used as raw materials. The structural evolution and decomposition processes of the precursors were investigated by powder X-ray diffraction, differential thermal analysis and thermogravimetric analysis. Crystalline Ca0.8Ba0.2Ti03:Pr(3+) could be obtained at 700°C. The photoluminescence properties of the samples were investigated using excitation and emission spectra. Ca0.8Ba0.2Ti03:Pr(3+) nanoparticles showed strong red emission, which could be assigned to the typical (1) D2 →(3) H4 transition of Pr(3+). Furthermore, the study found that sintering temperature and the introduction of Ba(2+) influence the decay time of persistent luminescence.