Numerical Investigation of Graphene as a Back Surface Field Layer on the Performance of Cadmium Telluride Solar Cell.

This paper numerically explores the possibility of ultrathin layering and high efficiency of graphene as a back surface field (BSF) based on a CdTe solar cell by Personal computer one-dimensional (PC1D) simulation. CdTe solar cells have been characterized and studied by varying the carrier lifetime, doping concentration, thickness, and bandgap of the graphene layer. With simulation results, the highest short-circuit current (Isc = 2.09 A), power conversion efficiency (h = 15%), and quantum efficiency (QE ~ 85%) were achieved at a carrier lifetime of 1 × 103 ms and a doping concentration of 1 × 1017 cm-3 of graphene as a BSF layer-based CdTe solar cell. The thickness of the graphene BSF layer (1 mm) was proven the ultrathin, optimal, and obtainable for the fabrication of high-performance CdTe solar cells, confirming the suitability of graphene material as a BSF. This simulation confirmed that a CdTe solar cell with the proposed graphene as the BSF layer might be highly efficient with optimized parameters for fabrication.

Sol-Gel Deposited Double Layer TiO2 and Al2O3 Anti-Reflection Coating for Silicon Solar Cell.

In this work, the deposition of double layer ARC on p-type Si solar cells was carried out by simple spin coating using sol-gel derived Al2O3 and TiO2 precursors for the fabrication of crystalline Si solar cells. The first ARC layer was created by freshly prepared sol-gel derived Al2O3 precursor using spin coating technique and then second ARC layer of TiO2 was deposited with sol-gel derived TiO2 precursor, which was finally annealed at 400 °C. The double layer Al2O3/TiO2 ARC on Si wafer exhibited the low average reflectance of 4.74% in the wavelength range of 400 and 1000 nm. The fabricated solar cells based on double TiO2/Al2O3 ARC attained the conversion efficiency of ~13.95% with short circuit current (JSC) of 35.27 mA/cm2, open circuit voltage (VOC) of 593.35 mV and fill factor (FF) of 66.67%. Moreover, the fabricated solar cells presented relatively low series resistance (Rs) as compared to single layer ARCs, resulting in the high VOC and FF.

Development of a Solar Cell Back Sheet with Excellent UV Durability and Thermal Conductivity.

The back sheet is one of the most important materials in photovoltaic (PV) modules. It plays an important role in protecting the solar cell from the environment by preventing moisture penetration. In the back sheet, the outermost layer is composed of a polyester (PET) film to protect the PV module from moisture, and the opposite layer is composed of a TiO2 + PE material. Nowadays, PV modules are installed in the desert. Therefore, methods to improve the power generation efficiency of PV modules need to be investigated as the efficiency is affected by temperature resulting from the heat radiation effect. Using a back sheet with a high thermal conductivity, the module output efficiency can be increased as heat is efficiently dissipated. In this study, a thermally conductive film was fabricated by mixing a reference film (TiO2 + PE) and a non-metallic material, MgO, with high thermal conductivity. UV irradiation tests of the film were conducted. The thermally conductive film (TiO2 + PE + MgO) showed higher conductivity than a reference film. No visible cracks and low yellowing degree were found in thermally conductive film, confirming its excellent UV durability characteristics. The sample film was bonded to a PET layer, and a back sheet was fabricated. The yellowing of the back sheet was also analyzed after UV irradiation. In addition, mini modules with four solar cell were fabricated using the developed back sheet, and a comparative outdoor test was conducted. The results showed that power generation improved by 1.38%.

Properties of CuInS2 Nano-Particles on TiO2 by Spray Pyrolysis for CuInS2/TiO2 Composite Solar Cell.

In this letter, for the absorption layer of a CuInS2/TiO2 composite solar cell, I­III­VI2 chalcopyrite semiconductor CuInS2 nano-particles were deposited by using spray pyrolysis method on TiO2 porous film. Their material characteristics including structural and optical properties of CuInS2 nano-particles on TiO2 nanorods were analyzed as a function of its composition ratios of Cu:In:S. Crystalline structure, surface morphology and crystalline size were also investigated by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM), and High-Resolution TEM (HRTEM), respectively. On the other hand, optical property was characterized by an UV-Visible Spectrophotometer. As a result, it was found that the size of CuInS2 nano-particles, which was formed at 300±5 °C, was smaller than 16 nm from HRTEM analyses, and it was identified that the CuInS2 particle size was increased as increasing the heat-treatment temperature and time. However, as the size of CuInS2 nano-particle becomes smaller, optical absorption edge of ternary compound film tends to move to the blue wavelength band. It turns out that the optical energy-band gap of the compound films was ranging from 1.48 eV to 1.53 eV.

Optimization of BBr3-Based Co-Diffusion Processes for Bifacial N-Type Solar Cells.

We report on the co-diffused bifacial N-type solar cells based on N-type Si wafers using the process of spin on doping (SOD, phosphorous source) and boron tribromide (BBr3) diffusion by atmospheric pressure chemical vapor deposition (APCVD). For bifacial co-diffusion, a phosphorous layer was deposited by SOD on the rear side of N-type Si wafer and a BBr3 as boron dopant source deposited by APCVD. Co-diffusion process was controlled by changing the flowrate of carrier N2 gas and drive-in temperatures. It was found that the fabricated bifacial co-diffused N-type solar cell with 2% H3PO4 doping, the flowrate of N2 carrier gas of 15 slm and drive-in temperature at 930°C exhibited the highest conversion efficiency of 15.8% with high open circuit voltage (V(oc)) of 593 mV. As compared to high H3PO4 concentrations (5% and 9%), the low H3PO4 concentration of SOD showed the higher sheet resistance and decreased in the thickness of N + emitter layer, resulting in the high V(oc), shunt resistance, fill factor and conversion efficiency of solar cells.

Nanoprecursor-Mediated Synthesis of Mg²âº-Doped TiO2 Nanoparticles and Their Application for Dye-Sensitized Solar Cells.

Surface-doping anatase TiO2 nanoparticles with Mg²âº were prepared via a novel synthetic method, and used as photoanodes for dye-sensitized solar cells (DSSCs). X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) image results indicate that the Mg²âº doping has no effect on the crystal phase and morphology of anatase TiO2. The shift in XRD peaks to higher angles, the absorption shift in UV-vis diffuse reflection spectra, and X-ray photoelectron spectroscopy (XPS) results indicate the incorporation of Mg²âº-ions into the TiO2 lattice. The as-prepared TiO2nanoparticles doped with a low concentration of ions is proven a superior photoanode material than pure anatase TiO2. The energy-conversion efficiency (1) of DSSC based on TiO2 nanoparticles doped with Mg²âº is at a maximum of 5.90%, corresponding to an efficiency improvement of 23.4% as compared to DSSC based on un-doped TiO2. This new synthetic approach using a nanoprecursor provides a simple and versatile method for the preparation of excellent photoanode materials for application in solar energy conversion devices.

Electrocatalytic behavior of calcium doped LaFeO3 as cathode material for solid oxide fuel cell.

La(1-x)Ca(x)FeO3 (X = 0.0, 0.2, 0.4, abbreviated as LCF) as cathode material for intermediate temperature solid oxide fuel cells (IT-SOFC) was synthesized by new route of glycine nitrate method. LCF materials were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), electrical and electrochemical impedance spectroscopy (EIS). The powder LCFs exhibited single phase with orthorhombic structure, highly porous and small nanoparticles with average size of 200-300 nm. The electrical conductivities of LCFs increased as increasing the Ca content and achieved the maximum electrical conductivity of 148 Scm(-1) for La0.6Ca0.4FeO3 (X = 0.4) at 550 degrees C. The improved conductivity of LCFs could be a promising cathode material for IT-SOFCs. In the impedance analysis of fabricated symmetry cell with the optimized La0.6Ca0.4FeO3 cathode and Ce0.8Sm0.2O3 (SDC) electrolyte, the minimum area specific resistance (ASR) of 0.15 omegacm2 was observed at 850 degrees C, which may due to the lowest activation energy (1.55 eV), resulting from the reduction of oxygen molecules into oxygen ions. It was found that calcium doping was essential to increase the charge carrier concentration of lanthanum iron oxide materials, resulting in the high conductivity at intermediate temperature.

Electrical and structural characterization of plasma polymerized polyaniline/TiO2 heterostructure diode: a comparative study of single and bilayer TiO2 thin film electrode.

A heterostructure was fabricated using p-type plasma polymerized polyaniline (PANI) and n-type (single and bilayer) titanium dioxide (TiO2) thin film on FTO glass. The deposition of single and bilayer TiO2 thin film on FTO substrate was achieved through doctor blade followed by dip coating technique before subjected to plasma enhanced polymerization. To fabricate p-n heterostructure, a plasma polymerization of aniline was conducted using RF plasma at 13.5 MHz and at the power of 120 W on the single and bilayer TiO2 thin film electrodes. The morphological, optical and the structural characterizations revealed the formation of p-n heterostructures between PANI and TiO2 thin film. The PANI/bilayer TiO2 heterostructure showed the improved current-voltage (I-V) characteristics due to the substantial deposition of PANI molecules into the bilayer TiO2 thin film which provided good conducting pathway and reduced the degree of excitons recombination. The change of linear I-V behavior of PANI/TiO2 heterostructure to non linear behavior with top Pt contact layer confirmed the formation of Schottky contact at the interfaces of Pt layer and PANI/TiO2 thin film layers.

Diode behavior of electrophoretically deposited polyaniline on TiO2 nanoparticulate thin film electrode.

An inorganic/organic hetrostructure diode was constructed by the electrophoretic deposition of the p-type polyaniline (PANI) on an n-type titanium oxide (TiO2) nanoparticulate thin film. The bonding and internalization of PANI to TiO2 nanoparticulate thin film were confirmed by the morphological, structural and optical studies of electrophoretically deposited PANI/TIO2 nanoparticulate thin film. The increased size of TiO2 nanoparticles indicated the well penetration of PANI molecules into the pores of mesoporous TiO2 nanoparticulate thin film. The XPS studies of PANI/TiO2 heterostructure exhibited the surface bonding and interaction between PANI molecules and TiO2 nanoparticles. The current-voltage (I-V) characterization of PANI/TiO2 heterostructure was carried out in the forward and the reverse bias at the applied voltage ranges from -1 V to +1 V with a scan rate of 2 mV/s. The constructed Pt/PANI/TiO2 heterostructure device established diodic behavior with non-linear nature of I-V curves.

Synthesis and characterization of high-purity silica nanosphere from rice husk.

The work reports the synthesis, characterization, and the properties of high-purity silica nanospheres from low-cost rice husk. Primarily, the rice husk was washed with distilled water (DW) and subjected to acid leaching to remove the impurities. The treated rice husk was annealed at different temperatures (620 and 900 degrees C) for varied time periods to achive the desirable silica nanospheres. The annealing temperature and time considerably affected the properties of the synthesized silica nanospheres. The morphology studies confirmed that the size of nanospheres were of approximately 50-60 nm. The photoluminesence studies revealed that the synthesized silica nanospheres showed less structural defects and good optical properties. On the basis of the formation and the characterization of silica nanospheres a possible mechanism was suggested. Inductively coupled plasma mass spectrometry (ICP-MS) analysis confirmed that the synthesized silica nanospheres contained approximately 99.93% purity.

N,N'-Dimethyl-N,N'-bis-(pyridin-2-yl)methane-diamine.

The title compound, C(13)H(16)N(4), consists of two pyridine rings which are linked by an N,N'-dimethyl-methane-amine chain. The pyridine rings adopt a twist conformation and the dihedral angle between them is 60.85 (5)°. The crystal packing is stabilized by weak C-H⋯π inter-actions.

Photocatalytic degradation of methylene blue dye under visible light over Cr doped strontium titanate (SrTiO3) nanoparticles.

Strontium titanate (SrTiO3) and chromium doped SrTiO3 (Cr/SrTiO3) were prepared by modified sol-gel method with the citric acid as a chelating agent in the ethylene glycol solution for the effective photodegradation of methylene blue dye under visible light irradiation. The synthesized doped and un-doped SrTiO3 nanoparticles were structurally characterized and their photoresponse performances for the efficient degradation of methylene blue dye have been demonstrated. After introducing the Cr on SrTiO3, UV-Vis absorption was appeared the red-shift at 566 nm from 392 nm as compare with bare SrTiO3. The photocatalytic degradation activity of Cr/SrTiO3 was significantly improved to 60% degradation of methylene blue in 3 h under visible light, which is approximately 5 times higher than that of the bare SrTiO3.

Carbon nanotube (CNT)-polymethyl methacrylate (PMMA) composite electrolyte for solid-state dye sensitized solar cells.

A novel carbon nanotube (CNT)-polymethyl methacrylate (PMMA) composite electrolyte was successfully synthesized by the thermal polymerization of methyl methacrylate (MMA) with CNTs for solid-state dye sensitized solar cells (DSSCs). The prepared CNTs-PMMA composite electrolytes were characterized by Fourior transformed-infrared (FT-IR) spectroscopy, field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and ionic conductivity. A strong bonding was observed between CNT and PMMA through ester bonding in the CNT-PMMA composite, resulting in the lowering of crystallinity and increasing the ionic conductivity of composite electrolyte. DSSCs fabricated with CNTs-PMMA composite electrolytes achieved relatively high conversion efficiency of 2.9% with an open circuit voltage (V(oc)) of 0.567 volt, short circuit current (I(sc)) of 8.9 mA/cm2 and fill factor of 61.8%, which is attributed to enhanced amorphicity and ionic conductivity due to the formation of strong bonding between CNT and PMMA molecules.

Thermally grown ZnO nanosheets for high efficiency dye-sensitized solar cells.

High efficiency dye-sensitized solar cells (DSSCs) were fabricated using ZnO nanosheet electrodes. ZnO nanosheets were synthesized on top of fluorine-doped tin oxide (FTO) glass using Zn(OAc)2 as a precursor in the gold catalyzed chemical vapor deposition (CVD) method at a temperature of 800-900 degrees C. The synthesized materials were characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and Raman and photoluminescence (PL) spectroscopy. Typical DSSCs with ZnO nanosheets achieved moderately good conversion efficiency eta of approximately 2.12% with short-circuit current density J(SC) = 3.56 mA/cm2, open-circuit voltage V(OC) = 0.831 V, and fill factor FF = 71%. The high J(SC) and eta are attributed to high dye absorption through high surface ZnO nanosheets, which increased the light harvesting. The lower recombination rate was also observed in the ZnO nanosheet electrodes, resulting in high values of V(OC) and FF in the DSSCs.

Synthesis of single-crystalline ZnO nanowires and their applications in dye-sensitized solar cells (DSSCs) with a solid polyethylene glycol (PEG) redox electrolyte.

We demonstrate for the first time ZnO nanowire dye-sensitized solar cells (DSSCs) with a solid-state poly (ethylene glycol) (PEG) redox electrolyte. From the current-voltage characteristics of this solid PEG electrolyte-based ZnO nanowire DSSCs, the open-circuit voltage and short-circuit current density, and fill factor were determined to be approximately 0.58 V, approximately 1.30 mA/cm2, and 0.31, respectively. We obtained a power conversion efficiency of approximately 0.24% under an incident irradiation of 100 mW/cm2, corresponding to air mass (AM) 1.5 global solar conditions. The solid-state DSSC experienced an efficiency that was approximately 0.1% lower than the efficiency a liquid electrolyte based ZnO nanowire DSSC.

Synthesis and characterization of ultrahigh crystalline TiO2 nanotubes.

Ultrahigh crystalline TiO2 nanotubes were synthesized by hydrogen peroxide treatment of very low crystalline titania nanotubes (TiNT-as prepared), which were prepared with synthesized TiO2 nanoparticles by hydrothermal methods in an aqueous NaOH solution. Thus, prepared ultrahigh crystalline TiO2 nanotubes (TiNT-H2O2) showed comparable crystallinity with high crystalline TiO2 nanoparticles. The details of nanotubular structures were elucidated by high resolution-transmission electron microscopy (HR-TEM), field emission-scanning electron microscopy (FE-SEM), energy-dispersive X-ray analysis in transmission electron microscopy (TEM-EDX), X-ray diffraction (XRD), photoluminescence (PL), and BET surface area. TiNT-H2O2 was found to be a multiwalled anatase phase only with an average outer diameter of approximately 8 nm and an inner diameter of approximately 5 nm and grown along the [001] direction to 500-700 nm long with an interlayer fringe distance of ca. 0.78 nm. The photocatalytic activity of TiNT-H2O2 was about 2-fold higher than those of TiNT-as prepared, synthesized TiO2 nanoparticles, and TiO2-P25 (Degussa) in the photocatalytic oxidation of trimethylamine gas under UV irradiation.

Characterization of Boron Diffusion Phenomena According to the Specific Resistivity of N-Type Si Wafer.

This paper is directed to characterize the boron diffusion process according to the specific resistivity of the Si wafer. N-type Si wafers were used with the specific resistivity of 0.5-3.2 omega-cm, 1.0-6.5 omega-cm and 2.0-8.0 omega-cm. The boron tribromide (BBr3) was used as boron source to create the PN junction on N-type Si wafer. The boron diffusion in N-type Si wafer was characterized by sheet resistance of wafer surface, secondary ion mass spectroscopy measurements (SIMS) and surface life time analysis. The degree of boron diffusion was depended on the variation in specific resistivity and sheet resistance of the bare N-type Si wafer. The boron diffused N-Si wafer exhibited the average junction depth of 750 nm and boron concentration of 1 x 10(19). N-type Si wafer with the different specific resistance considerably affected the boron diffusion length and life time of Si wafer. It was found that the lifetime of boron diffused wafer was proportional to the sheet resistance and resistivity. However, optimization process may necessary to achieve the high efficiency through the high sheet resistance wafer, because the metallization process control is very sensitive.

Hydrodechlorination of Silicon Tetrachloride to Trichlorosilane Over Ordered Mesoporous Carbon Catalysts: Effect of Pretreatment of Oxygen and Hydrochloric Acid.

This paper reports on the catalytic reaction for the conversion of silicon tetrachloride (STC) to trichlorosilane (TCS) over pretreated ordered mesoporous carbon (OMC) catalysts by oxygen (denoted as OMC-O2) and hydrochloric acid (denoted as OMC-HCl) at 300 degrees C under N2 atmosphere. The OMC-O2 shows significantly improved the surface area (1341.2 m2/g) and pore volume (1.65 cm3/g), which results in the highest conversion rate of 7.3% as compared to bare OMC (4.3%) and OMC-HCI (5.7%). It is found that the conversion rate of STC to TCS is proportional to the number of Si-O bond over OMC catalysts, which suggests that Si-O-C bond formation is crucial to the reaction as active sites. The O2 pretreatment seems to promote the generation of oxygenated species for the formation of Si-O-C.

Effect of TiO2 Particle Size on the Performance of Flexible Dye Sensitized Solar Cells.

The size TiO2 nanoparticles was controlled by changing the concentration of titanium tetraisopropanolate (TTIP) and utilized as light scattering particles in the efficient flexible photoelectrodes for flexible dye sensitized solar cells (DSSCs). The flexible photoelectrodes were prepared by TiO2 nanoparticles (-25 nm) paste with different concentrations of ethanolic TTIP solution. The addition of TTIP produced the bigger TiO2 nanoparticles, which significantly enhanced the dye absorption of flexible TiO2 photoelectrode. The fabricated flexible DSSCs showed the reasonable conversion efficiency of 2.50% with short circuit current (J(sc)) of 6.3 mA/cm2, open circuit voltage (V(oc)) of 0.720 V and fill factor (FF) of 0.55. The improvement in photovoltaic performance with 25 wt% TTIP might due to uniform distribution of small TiO2 nanoparticles over the big particles to lead the enhancement in the surface area, resulting in the high dye absorption and light harvesting efficiency.

Steam Treated Ordered Mesoporous Carbon Nanomaterials for Catalytic Conversion of Silicon Tetrachloride to Trichlorosilane.

The steam-pretreatment on ordered-mesoporous carbon (OMC) catalysts was conducted to improve the catalytic properties for silicon tetrachloride (STC) to trichlorosilane (TCS) conversion. The surface area, pore size and pore volume of OMC were significantly changed as a function of pretreatment temperature. The steam-pretreated OMC at 500 degrees C exhibited the high surface area (-1476.4 m2/g) and pore volume (1.89 cm3/g), which leads the highest conversion rate of 10.8% as compared to bare-OMC (4.3%) and the steam-pretreated OMC. The steam-pretreatment on OMC might increase active oxygenated species, which promoted the generation of active sites of C-O-Si-for high conversion of STC to TCS.