Study of the Optical, Electrical, Structural and Morphological Properties of Electrodeposited Lead Manganese Sulphide (PbMnS) Thin Film Semiconductors for Possible Device Applications

Semiconductor thin films of lead manganese sulphide (PbMnS) have been successfully deposited on florinated tin oxide (FTO) conductive glass substrate using an electrodeposition method. Lead acetate (Pb(CH3COO)2), manganese sulphate (MnSO4.H2O) and thiourea (CH4N2S) were the precursor used for cadmium (Cd2+), manganese (Mn2+) and sulphur (S2-) sources respectively. The concentration of manganese (Mn2+) was varied while keeping the concentrations of Pb2+ and S2- constant at 0.2 M and 0.1 M respectively. The deposited films were annealed at temperature of 250 oC and subjected for optical, electrical, structural and morphological characterizations. The results of the characterizations showed that the deposited thin films of PbMnS have high absorbance, high absorption coefficient throughout VIS and NIR regions. The band gap energy of the films is tuned to the order of 1.9 eV to 2.0 eV and tends to constant as concentration of Mn2+ increased. The electrical properties (electrical resistivity and conductivity) of the films are dependent on the concentration of Mn2+ and film thickness. The range of values of the electrical properties is found to be within the range of values for semiconductor materials. The XRD analysis revealed that the deposited thin films of PbMnS is crystalline but the crystallinity declined with increase in concentration of Mn2+. The SEM morphology showed that the surfaces of the films are highly homogeneous in nature and particle sizes are uniform on the substrate with the majority of the particles been spherical in shape. These observed properties exhibited by the deposited thin films of PbMnS make the films good materials for many optoelectronic and electronic applications such as solar cell, light emitting diode (LED), photodetector etc.

Preparation of ZnO/Bi2O3 Composites as Heterogeneous Thin Film Materials with High Photoelectric Performance on FTO Base

In recent years, ZnO nanomaterials have achieved great performance in solar energy applications. How to synthesize a ZnO nanocomposite structure with high photoelectric conversion efficiency has become an urgent problem to solved. In this paper, a narrow band gap bismuth trioxide (Bi2O3) coated on a ZnO nanoarray by magnetron sputtering was used to prepare a composite heterojunction ZnO/Bi2O3. Studies have found that ZnO/Bi2O3 exhibits excellent photoelectric conversion performance. By preparing a composite heterostructure of ZnO/Bi2O3, it can effectively compensate for the insufficient absorption of ZnO in the visible light range and inhibit the recombination of carriers within the material. The influence of Bi2O3 thickness on the microstructure and electronic structure of the ZnO/Bi2O3 composite structure was explored and analyzed. The energy gap width of the composite heterostructure decreases with the increase in the Bi2O3 thickness on the surface of the ZnO nanorod array. At the same time, the conductive glass composite film structure is simple to prepare and is very environmentally friendly. The ZnO/Bi2O3 composite heterogeneous material prepared this time is suitable for solar cells, photodetectors, photocatalysis and other fields.

CURE BEHAVIOR OF NANOSTRUCTURED HIERARCHICAL COMPOSITES WITH FUNCTIONALIZED CARBON NANOTUBES

Electrophoretic deposition is a promising technique to hybridize nanomaterials with conventional reinforcing materials for multifunctional applications. It utilizes the principle of electrophoresis, where electric potential drives charged particles dispersed in a liquid towards counter-charged substrates. Polymer matrix can be infused into the hybridized fibers to produce hierarchical polymer composites with reinforcements spanning several orders of magnitude in scale. This research addresses a key challenge associated with nanostructured composites produced by first dispersing the nanoscale reinforcement into the polymer matrix and then infusing into the fiber reinforcement (direct mix/infusion method). The key limitation is on the volume fraction of the nanoscale particles due to the drastic increase of the resin viscosity and the potential filtering effect of the particles during resin infusion. Our model system consists of an aqueous dispersion of carbon nanotubes (CNT) functionalized with a cationic polymer, polyethyleneimine (PEI), non-conductive glass fabric and epoxy resin. Amine functional groups of PEI are protonated under mildly acidic conditions, producing positively charged CNTs. A stable dispersion is formed through repulsive electrostatic forces among charged CNTs, which also facilitates deposition under applied electric fields. CNT-PEI films uniformly deposited via EPD on each filament throughout the fabric form a unique interface between reinforcing fiber and epoxy matrix. Concentrated amines from CNT-PEI coatings possibly alter the curing mechanism of infused epoxy resin, thereby creating the graded mechanical properties at the interface. In this study, curing kinetics and thermomechanical properties of epoxy resin are investigated with added PEI which provides stoichiometrically excessive amines. It is expected that the curing temperature profile can be designed to optimize the interfacial properties of electrophoretically processed CNT-PEI multiscale composites.

Fabrication of a stable light-activated and p/n type AgVO3/V2O5-TiO2 heterojunction for pollutants removal and photoelectrochemical water splitting

In this study, TiO2 nanorod arrays (TiO2) was fabricated and modified with the AgVO3 quantum dots (QDs) decorate on interfacing few-layer V2O5 to form a heterojunction material for removal pollutants and photoelectrochemical (PCE) water splitting. The AgVO3/V2O5-TiO2 nanorod arrays (AgVO3/V2O5-TiO2) synthesized by the secondary hydrothermal method were loaded with conductive glass, which facilitated the formation of one-dimensional (1D) nanorod and p-n junction structures. Through instrumentations, to investigate the structural, morphological, optical, photocatalytic and PCE characteristics of the materials. The TiO2 modified by AgVO3 and V2O5 can significantly improve the visible light optical absorption, the reduce the electron-hole pair binding rate and shorten the band gap (3.07-1.41eV) of TiO2. The resulting photocurrent density (116uA/cm2 ) and photodegradation efficiency (rate constant, k = 0.025min− 1) of AgVO3/V2O5-TiO2 are approximately 20 (6uA/cm2) and 5 times (0.005min− 1) higher than those of bare TiO2, respectively. The AgVO3/V2O5-TiO2 achieved a current density of 10mA at an overpotential of 246.2mV and exhibited excellent oxygen evolution reaction (OER) performance. The systematic PEC experiments concluded that the optimized of the TiO2 interface by AgVO3 and V2O5 could promote the separation and transport of charge carriers.

Hydrothermally growth of TiO2 Nanorods, characterization and annealing temperature effect

Titanium dioxide TiO2 nanorods were successfully grown on conductive glass FTO substrate using the hydrothermal method at a temperature of 160 oC. Surface topography, structure, and optical characteristics were studied according to the influence of annealing temperature (450, 550, and 650) oC. The surface topography results reveal that the TiO2 had nanorods structure with a tetragonal shape, and the rod diameter increases from 84.2 nm to 116.6 nm with increasing the annealing temperature. The crystal structure of the grown TiO2 NRs exhibits a high crystallinity of polycrystalline nature with anatase and rutile phases. The preferential orientation was along (204) plane for anatase tetragonal structure. AFM image shows an intense edge, uniform surface morphology, and increased grain diameter with annealing temperature. The optical properties of TiO2 NRs were investigated, and the absorption edge shows a blue shifting as the annealing temperature increases when considering the crystallinity and morphology changes. The energy band gap was found to be lower than 3 eV, which can be attributed to the presence of anatase and rutile phases with an increment range from 2.72 to 2.86 nm alongside the increase in the annealing temperature. The results indicate that the adopted hydrothermal method and the synthesized TiO2 NRs were suitable for photovoltaic and photocatalytic applications.