International Journal of Photoenergy

For optimum performance of the hydrogenated amorphous silicon/crystalline silicon (a-Si : H/c-Si) heterojunction solar cells, featuring a doping concentration, localized states, as well as thickness of emitter layer are crucial, since Fermi level, surface passivated quality, and light absorption have to be compromised themselves. For this purpose, the effect of both doping concentration and thickness of emitter layer was investigated. It was found that with gas phase doping concentration and emitter layer thickness of 3% and 7 nm, solar cell efficiency in excess of 14.6% can be achieved. For high gas phase doping concentration, the degradation of open-circuit voltage as well as cell efficiency was obtained due to the higher disorder in the emitter layer. The heavily doped along with thicker in thickness of emitter layer results in light absorption on short wavelength, then diminishing short-circuit current density.

It is difficult to deposit extremely thin a-Si:H layer in heterojunction with intrinsic thin layer (HIT) solar cell due to thermal damage and tough process control. This study aims to understand oxide passivation mechanism of silicon surface using rapid thermal oxidation (RTO) process by examining surface effective lifetime and surface recombination velocity. The presence of thin insulating a-Si:H layer is the key to get highVocby lowering the leakage current (I₀) which improves the efficiency of HIT solar cell. The ultrathin thermal passivation silicon oxide (SiO₂) layer was deposited by RTO system in the temperature range 500–950^°C for 2 to 6 minutes. The thickness of the silicon oxide layer was affected by RTO annealing temperature and treatment time. The best value of surface recombination velocity was recorded for the sample treated at a temperature of 850^°C for 6 minutes at O₂flow rate of 3 Lpm. A surface recombination velocity below 25 cm/s was obtained for the silicon oxide layer of 4 nm thickness. This ultrathin SiO₂layer was employed for the fabrication of HIT solar cell structure instead of a-Si:H, (i) layer and the passivation and tunneling effects of the silicon oxide layer were exploited. The photocurrent was decreased with the increase of illumination intensity and SiO₂thickness.

Cu₂ZnSnS₄is considered as the ideal absorption layer material in next generation thin film solar cells due to the abundant component elements in the crust being nontoxic and environmentally friendly. This paper summerized the development situation of Cu₂ZnSnS₄thin film solar cells and the manufacturing technologies, as well as problems in the manufacturing process. The difficulties for the raw material’s preparation, the manufacturing process, and the manufacturing equipment were illustrated and discussed. At last, the development prospect of Cu₂ZnSnS₄thin film solar cells was commented.

Shifting the threshold zone of road tunnels with semitransparent tension structures has shown itself to be an effective way of saving energy in regards to electricity consumption, maintenance, and construction materials used in the electrical lighting, thus lessening negative environmental impacts. Even though the shape of the tension structure has a major influence on energy savings, the optimal type of structure for each tunnel is often difficult to determine, because experiments using real tunnels are extremely expensive. It is thus necessary to find methods of doing this that are both reliable as well as economical. In this research study, three candidate structures were set up at the portal of a scale model of a real tunnel. The energy savings in each case were analyzed and compared. As a result, it was possible to formulate a new equation that calculates the energy savings in the threshold zone.

Te and Se layers were deposited on〈glass/FTO/flat-TiO₂〉by electrochemical deposition. The Te-Se-stacked layer was annealed at 200°C, and then, the migration of Te into the Se layer by annealing was confirmed using auger electron spectroscopy (AES), which was performed by Te doping on the Se layer. Au back contact was coated by vacuum deposition on the Te-doped Se layer, resulting in superstrate-structured solar cells of〈glass/FTO/flat-TiO₂/Se-doped Te/Au〉with a 0.50 V open-circuit voltage, 6.4 mA/cm²photocurrent density, 0.36 fill factor, and 1.17% conversion efficiency.

Self-organized TiO₂nanotubes (TNTs) with average inner diameter of 109 nm, wall thickness of 15 nm, and tube length of 7–10 μm were loaded with nickel oxide (NiO) nanoparticles via incipient wet impregnation method. The molar concentration of Ni(NO₃)₂·6H₂O aqueous solution varied in a range of 0.5 M–2.5 M. The samples were characterized for crystalline phase, morphology, topography, chemical composition, Raman shift, and UV-Vis diffusion reflection properties. The finding shows that the loading of NiO did not influence the morphology, structure, and crystalline phase of TNTs but it exhibited significant effect on crystallite size and optical absorption properties. Further, the solar-energy-driven the photocatalytic activity of NiO/TNTs and pure TNTs was evaluated by degrading methylene blue (MB). The results confirm that photocatalytic efficiency of NiO/TNTs is higher than that of TNTs.

Modification of TiO₂ by doping of a residue carbon and iron can give enhanced photoactivity of TiO₂. Iron adsorbed on the surface of TiO₂ can be an electron or hole scavenger and results in the improvement of the separation of free carriers. The presence of carbon can increase the concentration of organic pollutants on the surface of TiO₂ facilitating the contact of the reactive species with the organic molecules. Carbon‐doped TiO₂ can extend the absorption of the light to the visible region and makes the photocatalysts active under visible‐light irradiation. It was proved that TiO₂ modified by carbon and iron can work in both photocatalysis and photo‐Fenton processes, when H₂O₂ is used, enhancing markedly the rate of the organic compounds decomposition such as phenol, humic acids and dyes. The photocatalytic decomposition of organic compounds on TiO₂ modified by iron and carbon is going by the complex reactions of iron with the intermediates, what significantly accelerate the process of their decomposition. The presence of carbon in such photocatalyst retards the inconvenient reaction of OH radicals scavenging by H₂O₂, which occurs when Fe‐TiO₂ photocatalyst is used.

Nowadays a hot topic among the research community is the harnessing energy from the free sunlight which is abundant and pollution-free. The availability of cheap solar photovoltaic (PV) modules has to harvest solar energy with better efficiency. The nature of solar modules is nonlinear and therefore the proper impedance matching is essential. The proper impedance matching ensures the extraction of the maximum power from solar PV module. Maximum power point tracking (MPPT) algorithm is acting as a significant part in solar power generating system because it varies in the output power from a PV generating set for various climatic conditions. This paper suggested a new improved work for MPPT of PV energy system by using the optimized novel improved fractional order variable step size (FOVSS) incremental conductance (Inc-Cond) algorithm. The new proposed controller combines the merits of both improved fractional order (FO) and variable step size (VSS) Inc-Cond which is well suitable for design control and execution. The suggested controller results in attaining the desired transient reaction under changing operating points. MATLAB simulation effort shows MPPT controller and a DC to DC Luo converter feeding a battery load is achieved. The laboratory experimental results demonstrate that the new proposed MPPT controller in the photovoltaic generating system is valid.

The photodecolourization of Direct Yellow 9, a member of the group of azo dyes which are commonly used in the various branches of the industry, was investigated. The photostability of this dye was not previously examined. Photocatalytic degradation method was evaluated. Solar simulated light (E=500 W/m²), titanium dioxide, and zinc oxide were used as irradiation source and photocatalysts, respectively. Kinetic studies were performed on a basis of a spectrophotometric method. Degradation efficiency was assessed by applying high performance liquid chromatography. Disappearance of a dye from titanium dioxide and zinc oxide surfaces after degradation was confirmed by thermogravimetry and Raman microscopy. Direct Yellow 9 was found to undergo the photodegradation with approximately two times higher efficiency when zinc oxide was applied in comparison with titanium dioxide. A simple and promising way to apply the photocatalytic removal of Direct Yellow 9 in titanium dioxide and zinc oxide suspensions was presented.

Thin film solar cells based on monocrystalline Si films are transferred to a glass superstrate. Chemical vapor deposition serves to epitaxially deposit Si on quasi‐monocrystalline Si films obtained from thermal crystallization of a double layer porous Si film on a Si wafer. A separation layer that forms during this crystallization process allows one to separate the epitaxial layer on top of the quasi‐monocrystalline film from the starting Si wafer. We presently achieve an independently confirmed solar cell conversion efficiency of 9:26%. Ray tracing studies in combination with electrical device simulation indicate an efficiency potential of around 17% using simple device processing and moderate assumptions on minority carrier lifetime and surface recombination.