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Carbon-based counter electrodes of dye-sensitized solar cells (DSSCs) such as carbon black-graphite composite (CB/Gr) have received unprecedented interest in recent years due to their ease of fabrication, good corrosion resistance, and low cost compared to platinum (Pt) electrodes. However, the poor surface adherence between the carbon counter electrodes (CE) and FTO substrate, low surface area, and poor inter-particle connection between the carbon materials have consistently become a major challenge. In order to overcome these issues, we have fabricated CB/Gr by incorporating binders of titanium (IV) isopropoxide (TTIP), and zirconium (IV) dioxide (ZrO2) as the counter electrodes for the DSSC. The performance of the CE is characterized by four-point probe conductivity measurement, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS), and current density voltage (J-V) characteristics. The results revealed that incorporating binders to the CB/Gr has improved the series resistance (RS) and charge transfer resistance (RCT), which enhances the short-circuit current density (JSC), fill factor (FF), and the power conversion efficiency (PCE) of the device. The TTIP binder in CB/Gr CE exhibited superior performance in DSSC is largely attributed to the formation of TiO2 in situ with small particle size of about 100 nm, leading to enhanced intimate contact between the carbon materials, high surface area, and better surface adherence between counter electrode and the FTO substrate. Our findings, thereby, offer the possibility to engineer and optimize the energy levels of CE in an effort to develop a high-performing DSSC counter electrode.

Calcium (Ca) and lanthanum (La) doping into mesoporous TiO2 prevents nucleation and growth of particles during synthesis and calcination at high temperature, resulting in smaller particle sizes and a decrease in the band gap of TiO2. These collectively have a positive affect on the efficiency of dye-sensitized solar cells (DSSCs) when employed as the anode. When designing an effective DSSC anode, the efficiency of dye adsorption must also be considered. This work investigates the adsorption properties of N719 dye onto La and Ca doped mesoporous TiO2 anodes for DSSCs. Near edge X-ray absorption fine structure spectroscopy (NEXAFS) identified the presence of La and Ca dopants in the TiO2 nanoparticles. Performance of DSSCs with Ca and La doped mesoporous TiO2 anodes demonstrated that doping of TiO2 enhances the overall efficiency of the devices. Both doped TiO2 nanoparticles showed higher dye adsorption concentration than that of pure TiO2, as shown in Brunauer-Emmett-Teller (BET) characterization. By employing Langmuir and Freundlich isotherms, dye adsorption behaviour was modelled. Pure and Ca doped TiO2 demonstrated good correlation to both isotherms, whereas La doped TiO2 only showed good correlation with Langmuir isotherm. Irrespective of its single layer adsorption kinetics, 0.1 mol.% La doped TiO2 has shown the highest dye adsorption and efficiency due to increase in surface area and oxygen vacancies induced by La doping.

A hybrid photoanode material consisting of reduced graphene oxide–anatase titanium dioxide (rGO–anatase TiO2) nano-composite particles was produced by mixing an rGO solution into a TiO2 solution. The hybrid particles were then electrophoretically deposited (EPD) onto a fluorine-doped tin oxide (F:SnO2) coated (FTO) glass substrate to form the novel photoanode structure for a dye-sensitized solar cell (DSSC). Incorporation of graphene materials (i.e., the rGO flakes) into the hybrid photoanode increases the dye absorption ability, light harvesting and eventually the photocurrent-density (j). At the optimal proportion of rGO, the solar cell showed a short-circuit current density $$ \left( {j_{\text{SC}} } \right) $$ of 18.37 mA cm−2, an open-circuit voltage $$ \left( {V_{\text{OC}} } \right) $$ of 0.61 V, and a fill-factor (FF) of 52.1% with a power conversion efficiency (PCE) of 6.52%. The hybrid photoelectrode produced by electrophoretic deposition of the rGO-modified TiO2 solution shows excellent photoelectrochemical properties.

The interfacial compatibility between the graphite/carbon black composite counter electrode (Gr/CB CE) and the perovskite layer is a crucial determinant of the performance of the hole-transport-layer-free carbon-based perovskite solar cells, and judicious selection of the Gr/CB CE application method is essential for achieving an optimum contact. In this work, three different types of Gr/CB CEs application methods are investigated: (1) deposition of Gr/CB on the fluorine-doped tin oxide (FTO) substrate, followed by clamping to the perovskite layer, (2) direct deposition of Gr/CB onto the perovskite layer, and (3) deposition of Gr/CB onto the PbI

In this article, we present the data collected from the fabricated carbon black-graphite counter electrode for dye-sensitized solar cells (DSSC) by incorporating binders such as titanium (IV) isopropoxide (TTIP), and zirconium (IV) dioxide (ZrO2). The addition of binders to the carbon black-graphite composite (CB/Gr) can drastically improve the adherence between the counter electrodes and the fluorine-doped tin oxide (FTO) substrate, surface area and the interparticle connection between the carbon materials. These data are presented which comprise of the resistivity measurements, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX), and near-edge X-ray absorption fine structure (NEXAFS). The collection of this data was performed at room temperature. Detailed analysis of the data can be found in [1].

CH3NH3PbI3 (MAPbI3) perovskite layers can be obtained by thermal annealing thin films of the intermediate dimethyl sulfoxide (DMSO) intercalated complex, MA2Pb3I8·2DMSO. In the present work, the fo...

In this work, we investigated the morphology, electrical conductivity, catalytic properties, and binding energies of electronic states of a system consisting of acetylene carbon black (AB) and graphite as efficient and low-cost counter electrodes (CEs) for dye-sensitized solar cells (DSSCs), where ratios of AB to graphite of 0:1, 1:3, 1:1, 3:1, and 1:0 were investigated. These carbon-based CEs were characterized using four-point probe conductivity measurement, field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NAXAFS), electrochemical impedance spectrum (EIS), and current-voltage (I-V) performance. Introduction of small AB particles into graphite paste enhanced the electronic conductivity of AB-graphite composite due to the bridging of the graphite flakes for electrocatalytic activity of triiodide reduction. AB particles also offer large surface area to provide high electrochemical performance in DSSCs. The overall highest power conversion efficiency of 5.06% was achieved for the DSSC fabricated with a CE consisting of AB-graphite ratio of 3:1, which is comparable to the DSSC performance with conventional platinum (Pt) CE. These findings suggest that AB and graphite composite could be a promising CE for low-cost DSSCs.

In this work, we investigate how Al and Mg doped mesoporous TiO2 layers can improve the power conversion efficiency (PCE) of perovskite solar cells (PSCs) with respect to undoped mesoporous TiO2. The PSC configuration used in this study consists of mesoscopic structure with CH3NH3PbI3 as the perovskite absorber. A PSC with optimized mol% of Al and Mg doped mesoporous TiO2 layers has been shown to achieve up to 22% higher efficiency than that of pure TiO2. While the Mg doping only enhances the open-circuit voltage (VOC), the Al doping effectively enhances the VOC, the short-circuit current density (JSC), and the fill factor (FF). The occupancy of the doped metals in the lattice is confirmed by XRD, EDX, and XPS. The Mg doping increases the band gap of TiO2 while the Al doping decreases it. The wide band gap in Mg doped TiO2 reduces the electron and hole recombination rate, thus increasing the JSC and VOC. By Al doping, deep trap sites in the TiO2 are eliminated, and this effectively reduces the recombination losses and in turn, increases the JSC. The enhanced electron-hole generation rate attributed to the decrease in the band gap of Al doped TiO2 also increases the JSC. In addition, there is an enhancement on the electron mobility by the presence of Al metal and this gives an increase in the FF. The results have demonstrated the possibility of improving the PCE of PSCs by fine tuning the band gap of mesoporous TiO2.

A dye-sensitized solar cell (DSSC) photocurrent efficiency (PCE) could be increased by 40.9% when the dye adsorbing TiO2 layer was introduced with reduced graphene oxide (rGO) layers. Thickness of rGO layer and number of rGO layers in the TiO2 anode were optimized. TiO2 and rGO were deposited on FTO substrate by electrophoretic deposition (EPD). The thickness of the rGO containing TiO2 anode was kept constant (10–11 μm) at all the times. Three rGO layers containing TiO2 anode has shown the highest PCE of 6.2%. rGO incorporation improved electron transfer that countered recombination losses hence increasing photocurrent density (JSC) of the DSSC.

A compact layer of TiO2, between FTO and mesoporous TiO2layer of DSSC anode, has the ability to reduce the electron recombination while mesoporous TiO2layer functions to collect and transport electrons injected by the photoexcited dye. In enhancing the desired functions of compact and mesoporous TiO2, we study the effects of co-doping it with Mg, Eu, and La. MgLa co-doped TiO2as compact layer has demonstrated higher efficiency due to its increased oxygen vacancies and smaller particle size which results reduced recombination. The combination of pure and co-doped TiO2nanoparticles to be selected as either compact or mesoporous layer of DSSC anode depends on their respective properties, as demonstrated in this paper.

We have computationally designed and characterized a series of new organic D−π−A architected dyes that have originated from cyanidin, which is vastly available in nature, for effective sensitization of DSSCs with absorption spectra extending up to near infrared region. Cyanidin acts as the donor group while cyanoacrylic acid and thieno [3, 2-b] thiophene are employed as the acceptor and π-spacer, respectively. Sensitization performance, depending on the substituted position of the π-spacer-acceptor (π-A) combination on cyanidin molecule, is examined by the results of density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. The calculated data of free energy change driving force ( Δ G inject ), electron regeneration driving force ( Δ G regen ), open circuit potential eV OC and light harvesting efficiency (LHE) suggest two preferred substitutions of π-A combination to cyanidin molecule that leads to an efficient DSSC. At LUMO the designed sensitizers have denser electron cloud towards acceptor group that leads to an efficient electron injection process. All π-A substitutions resulted a broader absorption spectrum with a redshift up to 2500 nm which is a significant improvement compared to the vast majority of reported sensitizers.

Although efficiency of Dye Sensitized Solar Cell (DSSC) is still below the performance level of the market dominance silicon solar cells, in the last two decades DSSC has gathered sufficient interests because of the simplicity in device fabrication and low material cost, and therefore, DSSC is providing a possibility of solar cells production at a low entry cost. This review presents the research progress made in the implementation of natural pigments in DSSC. These pigments function as dye sensitizers and they play a major role in DSSC by absorbing light, and supplying electrons to the semiconductor matrixes in the cell. The common choices of dyes are the metal complexes, organic and/or natural dyes. A better efficiency with higher durability is observed for DSSC using metal complexes and organic dyes, however, the process of synthesizing these dyes is laborious, costly, and involves the use of toxic materials. As an alternative, natural pigments (dyes) found in plants such as anthocyanin, carotenoid, aurone, chlorophyll, tannin, betalain and many others are accepted as dyes in DSSCs. These natural pigments are easily obtained from fruits, flowers, leaves, seeds, barks and various parts of plants. Despite the limited performance of natural dyes, the prevailing advantages of natural dyes include high absorption coefficients, high light harvesting efficiency, low cost extraction and low toxicity. This review provides insight into the usage of the various natural pigments as sensitizers, the techniques to improve the pigments performance in DSSC, an outlook on the developmental work on the application of natural pigments in DSSC and their limitation. Additionally, the paper discusses the overall operation principle and the recent developments of each component of DSSC, as well as, comparing the material cost between natural dye and synthetic dye DSSC.

Doping is a method whereby small amounts of impurities are introduced into the lattice of a material and is employed for improving the efficiency of dye-sensitized solar cells (DSSCs) via modification of the semiconductor material. Co-doping, which involves doping with more than one type of impurity, is typically used over doping owing to its unique effects on the short-circuit current and open-circuit voltage; the different types of added impurities can exert a synergy effect in enhancing the performance of DSSCs. Of particular interest is the study of the effects of the ionic radii of co-dopants on the performance of DSSCs that is not well understood to date. Thus, in this paper, TiO 2 was co-doped with lanthanum and magnesium, calcium, or aluminium at respective contents of 0.5 mol%. The co-doped TiO 2 and pure TiO 2 powders were prepared by sol–gel. Mg-La co-doped TiO 2 -based DSSC displayed the highest efficiency ( i.e. , 6.60%) and Al-La co-doped TiO 2 -based DSSC displayed the lowest efficiency. Among the dopants studied herein, aluminium ion has the smallest ionic radius. Thus, aluminium ions could easily enter the lattice structure of TiO 2 , generating a high concentration of holes that led to the decrease of electron transport and photocurrent, hence lower DSSC efficiency.

ZnO@TiO2 core–shell nanostructures have been manipulated with metal ion dopants to create DSSC photoanodes with reduced charge transfer recombination. ZnO and TiO2 were modified by doping with Cd and Mg, respectively, resulting in a reduction in the band-gap for Cd:ZnO and an increase in the band-gap for Mg:TiO2. A series of core–shell nanostructures based on a ZnO or a Cd:ZnO core and TiO2 or a Mg:TiO2 shell have been investigated as DSSC photoanodes. In another series, the core–shell materials were reversed for complete evaluation of our hypothesis. The structures of the core–shell nanoparticles, optoelectronic and interfacial charge transfer of the DSSCs were analyzed by XRD, SEM, TEM, XPS, Mott-Schottky experiment, UV–vis DRS, J–V and EIS measurements. The power conversion efficiencies (PCEs) of DSSCs based on these core–shell structures were observed to depend on the flat band of the shell oxide relative to that of the core oxide. DSSCs with Cd:ZnO@Mg:TiO2 and Cd:ZnO@TiO2 photoanodes achieved Voc and FF values comparable to those of DSSCs with TiO2 anodes. A moderate energy gradient and high potential barrier in these core–shell structures resulted in longer effective electron lifetimes and lower electron recombination in the corresponding DSSCs. The low PCE registered for DSSCs with anodes of Cd:ZnO@Mg:TiO2 and Cd:ZnO@TiO2 were attributed to the presence of a high proportion of rutile phase, caused by sintering at 650 °C and lower dye adsorption as a result larger particle sizes caused by Cd doping.

Natural dye sensitizers from Ixora coccinea (anthocyanin) and Bougainvillea glabra (betalain) flowers were prepared in five different ratios of ethanol to water (0, 30, 50, 70, and 90 % ethanol), and the effect of dye aggregation toward dye sensitized solar cell (DSSC) performance was evaluated. As the concentration of ethanol increases, the tendency of dye molecules to aggregate increased in Ixora dye extracts while no definite trend was observed in Bougainvillea dye extracts. The best DSSC performances of Ixora and Bougainvillea dyes exhibited by extracts in 70 % ethanol and 0 % ethanol are 0.58 ± 0.02 and 0.25 ± 0.02 %, respectively. Both high conversion efficiencies were ascribed to high electron density and low charge transfer resistance. From this study, it was revealed that the performances of DSSC could be affected by the formulation of dye aggregation on the TiO2 surface.

Natural dyes from Ixora coccinea (RX) and Bougainvillea sp. (BG) were extracted and these individual dyes as well as the cocktail dye of RX and BG (1:1 v/v ratio) were investigated as dye sensitizers in dye sensitized solar cells (DSSCs). To analyze the capability of the dyes, various characterization methods were deployed such as incident photon-to-current efficiency (IPCE), current-to-voltage (I-V) characteristics, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). It was found that DSSC sensitized with RX performed the best with η = 0.76%, followed by the cocktail dye (η = 0.40%) and BG (η = 0.21%). This best overall performance of RX was attributed to the charge transport resistance (Rtr = 3.89 Ω), with the highest electron density (ɳs = 9.45 × 1028) and effective diffusion coefficient (Deff = 2.43 × 10− 8 m2/s), which accounted for high Jsc. Co-dominance performance of DSSC sensitized with cocktail dye was observed where the cocktail dye has demonstrated an improved Voc as compared to RX and improved Jsc against BG, suggesting individual influence from both dyes.

An innovative type of composite photoanode consisting of a TiO 2 nanofibre (NF) layer sandwiched between two TiO 2 nanoparticle (NP) layers has been fabricated and tested in dye sensitized solar cells. After sintering, the nanofibres in the layer have turned to an elongated bead type nanostructure. DSSCs fabricated with the TiO 2 NP/NF/NP composite three layer photoanode sensitized with N 719 Ruthenium dye and a electrolyte solution consisting of tetrapropylammonium iodide and iodine dissolved in acetontrile and ethylene carbonate co-solvent showed the highest efficiency of 7.09% where as the DSSC with TiO 2 nano particle photoanode and the same electrolyte showed an efficiency of 5.38%. The increased efficiency has been attributed to enhanced light harvesting due to scattering within the TiO 2 nanofibre structure. The efficiency of the highest efficiency DSSC has been further enhanced by using the “mixed cation effect” where the single iodide salt, Pr 4 NI, in the electrolyte has been replaced by two iodide salts KI and Pr 4 NI resulting an efficiency of 8.80%. The combined use of the TiO 2 three layer composite photoanode and the mixed cation iodide salt containing electrolyte represents an impressive efficiency enhancement by 64% compared to a corresponding DSSC made with TiO 2 nanoparticle (NP) photoanode and an electrolyte with the single iodide salt Pr 4 NI.

The effect of Lanthanum ions (La3+) on charge trapping in dye-sensitized solar cell (DSSC) photoanodes has been investigated with doped and surface-treated TiO2 nanoparticles. Doped nanoparticles consisting of 0.5 mol.% Mg and La co-doped TiO2, 0.5 mol.% Mg doped TiO2 and pure TiO2 were synthesized by the sol gel method. Surface-treated nanoparticles of Mg doped TiO2 and pure TiO2 were prepared by ball milling in 0.05 M aqueous La3+ solution. All materials were analyzed by XRD, XPS and UV–Vis DRS. Cell performance, surface free energy state changes and electron injection efficiency of DSSCs based on these nanoparticles were evaluated using current –voltage measurements, EIS and Incident photon to current conversion efficiency. Doped materials had La and Mg ions incorporated into the TiO2 lattice, while no lattice changes were observed for the surface-treated materials. Less visible light was absorbed by treated oxides compared with doped oxide samples. The overall power conversion efficiencies (PCE) of DSSC photoanodes based on doped materials were twice those of photoanodes fabricated from treated nanoparticles. Doping establishes deep traps that reduce the recombination of electron–hole (e–h) pairs. Conversely, the presence of absorbed oxygen in treated materials enhances e–h recombination with electrolyte at surface trap sites.

In this work, we have investigated the performance of acetylene carbon black/graphite (AB/G) composite counter electrodes (CEs) by incorporating TiO2 as a binder in dye-sensitized solar cells (DSSCs). We obtained five types of composite CE films at different weight ratios of 0:1, 1:3, 1:1, 3:1 and 1:0 by adding a constant amount of TiO2 to a mixture of AB/G. The performance of the composite electrodes was assessed by using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electrochemical impedance spectroscopies and photocurrent density–voltage characteristics. The results have shown enhanced DSSC efficiency due to improved charge transfer properties of the CE when adding TiO2. TiO2 enhances the binding of the electrode to the substrate. AB/G/TiO2 composites show superior overall results compared to AB/TiO2 and G/TiO2. Since AB has high catalytic activity and surface area, as the AB content of the composite is increased, the electrochemical properties of the CEs are improved. The DSSC with AB:G (3:1) exhibited the maximum power conversion efficiency (PCE) of 5.9% with the highest fill factor (FF) of 0.55, which are comparable to those DSSCs employing platinum CEs with PCE of 6.2% and FF of 0.67.

TiO 2 is a technologically important, naturally occurring, low cost material used in energy, environmental, health and many other applications. This paper reports the possibility of using commercial TiO 2 in several different applications. The efficiency of a silver nanoparticle incorporated TiO 2 dye sensitized solar cell increased by 27% evidently due to the plasmonic effect. In a dye sensitized solar cell when nanopowder TiO 2 photoanode was replaced by a composite TiO 2 photoanode containing TiO 2 nanopowder and TiO 2 nanofibres, the cell efficiency enhanced by more than 30%. In an electrochromic device of configuration, FTO glass/TiO 2 /Poly (methylmethacrylate) electrolyte/SnO 2 /FTO glass, an impressive reversible colour change was observed. Mg rechargeable battery fabricated with a TiO 2 cathode exhibited a discharge capacity of 220 mAh g -1 showing that Mg ++ can be reversibly intercalated in to the TiO 2 structure. An electrospun nanofibre membrane prepared from a biodegradable polymer and functionalized with TiO 2 nano powder was capable of removing arsenic (As) from drinking water efficiently.

The use of anthocyanin dyes extracted from epidermal leaves of Tradescantia spathacea (Trant) and petals of Ixora coccinea (IX) was evaluated in the application of dye-sensitized solar cells (DSSCs). Subsequently, cocktail anthocyanin dyes from these dyes were prepared and how they enhanced the cell’s overall performance was assessed using five different volume-to-volume ratios. Cocktail dyes absorbed a wider range of light in the visible region, thus increasing the cell efficiencies of the cocktail dyes when compared to the DSSC sensitized by individual dyes. The surface charge (zeta-potential), average size of aggregated anthocyanin molecules (zetasizer), and anthocyanin stability in different storage temperatures were analyzed and recorded. Lower size of aggregated dye molecules as revealed from the cocktail dyes ensured better adsorption onto the TiO2 film. Tradescantia/Ixora pigments mixed in 1 : 4 ratio showed the highest cell efficiency of η=0.80%, under the irradiance of 100 mW cm−2, with a short-circuit current density 4.185 mA/cm2, open-circuit voltage of 0.346 V, and fill factor of 0.499. It was found that the desired storage temperature for these cocktail dyes to be stable over time was −20°C, in which the anthocyanin half-life was about approximately 1727 days.

An improvement in the efficiency of Ixora ( Ixora sp. (Rubiaceae)) floral dye sensitized solar cells (DSSCs) has been achieved by diminishing the pigment’s interactions. Liquid column chromatography (LCC) separated the dye components, namely aurone, pelargonidin, and derivatives of cyanidin & malvidin, showed improved photovoltaic performance when compared to cells sensitized by the original dye extract of Ixora. The LCC separated dye components were analyzed using UV–Vis, fluorescence and Fourier transform infrared (FTIR) spectroscopic studies. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO) and band gaps of the dyes were investigated. The DSSC prepared with the LCC separated dye showed energy conversion efficiencies (ECEs) ranging from 0.203% to 0.951%, whereas the original Ixora dye sensitized cell showed an ECE of 0.381%. Transient photovoltage (TPV) measurements and electrochemical impedance spectroscopy (EIS) were used to elucidate the photovoltaic parameters.

We have tailored the extraction solvent of natural anthocyanin pigments from Ixora coccinea flower to lower charge transport resistance and enhance effective electron diffusion coefficient as well as absorption properties in DSSC sensitization. Six different extraction solvents were used in this study, namely, absolute ethanol, 70 % ethanol, acetone, dimethyl formamide, dimethyl sulfoxide, and distilled water. Dimethyl formamide was found to be able to extract the most anthocyanins from the Ixora flower, followed by dimethyl sulfoxide, acetone, absolute ethanol, 70 % ethanol, and distilled water, respectively. Dye-sensitized solar cells were fabricated using these extracted dyes as sensitizers and the cell performances were measured and characterized. The dye-sensitized solar cell equipped with a dye sensitizer extracted in 70 % ethanol achieved the highest conversion efficiency (ɳ = 0.50 ± 0.04 %) owing to its highest electron diffusion coefficient and lowest transport resistance in the TiO2/dye/electrolyte interface. This was followed by the cell equipped a with dye sensitizer extracted in acetone (ɳ = 0.30 ± 0.04 %), absolute ethanol (ɳ = 0.27 ± 0.01 %), dimethyl formamide (ɳ = 0.17 ± 0.01 %), dimethyl sulfoxide (ɳ = 0.16 ± 0.01 %), and distilled water (ɳ = 0.09 ± 0.003 %) in conversion efficiency performances, respectively. This study provides an insight into the importance of choosing the right medium for both dye extraction as well as the favorable solvent medium for dye adsorption onto TiO2.

Aim The aim of this study was to investigate the sensitivity of the trajectory log file based quality assurance to detect potential errors such as MLC positioning and gantry positioning by comparing it with EPID measurement using the most commonly used criteria of 3%/3 mm. Materials and methods An in-house program was used to modified plans using information from log files, which can then be used to recalculate a new dose distribution. The recalculated dose volume histograms (DVH) were compared with the originals to assess differences in target and critical organ dose. The dose according to the differences in DVH was also compared with dosimetry from an electronic portal imaging device. Results In all organs at risk (OARs) and planning target volumes (PTVs), there was a strong positive linear relationship between MLC positioning and dose error, in both IMRT and VMAT plans. However, gantry positioning errors exhibited little impact in VMAT delivery. For the ten clinical cases, no significant correlations were found between gamma passing rates under the criteria of 3%/3 mm for the composite dose and the mean dose error in DVH (r 0.05); however, a significant positive correlation was found between the gamma passing rate of 3%/3 mm (%) averaged over all fields and the mean dose error in the DVH of the VMAT plans (r = 0.59, P Conclusions This study has successfully shown the sensitivity of the trajectory log file to detect the impact of systematic MLC errors and random errors in dose delivery and analyzed the correlation of gamma passing rates with DVH.

Chlorophyll and xanthophyll dyes extracted from a single source of filamentous freshwater green algae (Cladophora sp.) were used to sensitize dye sensitized solar cells and their performances were investigated. A more positive interaction is expected as the derived dyes come from a single natural source because they work mutually in nature. Cell sensitized with mixed chlorophyll and xanthophyll showed synergistic activity with improved cell performance of 1.5- to 2-fold higher than that sensitized with any individual dye. The effect of temperature and the stability of these dyes were also investigated. Xanthophyll dye was found to be more stable compared to chlorophyll that is attributed in the ability of xanthophyll to dissipate extra energy via reversible structural changes. Mixing the dyes resulted to an increase in effective electron life time and reduced the process of electron recombination during solar cell operation, hence exhibiting a synergistic effect.

Two symmetrical star-shaped hole transporting materials (HTMs), i.e. FA-MeOPh and TPA-MeOPh with a fused triphenylamine or triphenylamine core and diphenylethenyl side arms were synthesized. FA-MeOPh showed a strong molar absorption coefficient and a red-shifted absorption compared with TPA-MeOPh because of its planar configuration. The power conversion efficiency (PCE) of the perovskite solar cells based on FA-MeOPh and TPA-MeOPh is about 11.86% and 10.79%, in which the efficiency of former is comparable to that (12.75%) of spiro-OMeTAD based cell. The high photocurrent (18.39 mA cm(-2)) of FA-MeOPh based solar cell relative to TPA-MeOPh based one may be attributable to the enhanced absorption in the near-IR region for mp-TiO2/CH3NH3PbI3/HTM based cell. The high mobility and low series resistance of mp-TiO2/CH3NH3PbI3/FA-MeOPh based cell led to the high fill factor (0.698) of FA-MeOPh based solar cell relative to TPA-MeOPh based one (0.627). In addition, the FA-MeOPh based cell showed a relative stability under light soaking for 250 h. The high efficiency, relative stability, synthetically simple and inexpensive materials as the HTMs hold promise to replace the expensive spiro-OMeTAD.

Natural dyes have become a viable alternative to expensive organic sensitizers because of their low cost of production, abundance in supply, and eco-friendliness. We evaluated 35 native plants containing anthocyanin pigments as potential sensitizers for DSSCs. Melastoma malabathricum (fruit pulp), Hibiscus rosa-sinensis (flower), and Codiaeum variegatum (leaves) showed the highest absorption peaks. Hence, these were used to determine anthocyanin content and stability based on the impacts of storage temperature. Melastoma malabathricum fruit pulp exhibited the highest anthocyanin content (8.43 mg/L) followed by H. rosa-sinensis and C. variegatum. Significantly greater stability of extracted anthocyanin pigment was shown when all three were stored at 4∘C. The highest half-life periods for anthocyanin in M. malabathricum, H. rosa-sinensis, and C. variegatum were 541, 571, and 353 days at 4∘C. These were rapidly decreased to 111, 220, and 254 days when stored at 25∘C. The photovoltaic efficiency of M. malabathricum was1.16%, while the values for H. rosa-sinensis and C. variegatum were 0.16% and 1.08%, respectively. Hence, M. malabathricum fruit pulp extracts can be further evaluated as an alternative natural sensitizer for DSSCs.

This paper describes a double layered co-sensitization in dye sensitized solar cells (DSSCs) by using natural pigments from Ixora flower (Ixora sp. (Rubiaceae)) and the outer dark purple skin of ‘Kembayau’ (Canarium odontophyllum) fruit. UV–vis absorption data revealed that both dyes were anthocyanins. Co-sensitization was done by first adsorbing the dye from C. odontophyllum into TiO2 electrode by dipping, and then by removing adsorbed dye of the top layer of TiO2 using a de-sorption solution before the Ixora sp. dye was allowed to adsorb. Power conversion efficiency of the co-sensitized solar cell was 1.55%. The conversion efficiencies of DSSCs sensitized with Ixora sp. , C. odontophyllum and the mixture of both dyes (1:1) were 0.96%, 0.59% and 1.13% respectively. The superior conversion efficiency achieved by layered co-sensitization is attributed to the high adsorption capacities of Ixora sp. and C. odontophyllum, and the homogeneous monolayer adsorption of Ixora sp. as revealed by Freundlich and Langmuir adsorption isotherms.

The active constituents of Canarium odontophyllum (COP) were investigated experimentally and theoretically for dye sensitized solar cell (DSSC) application. Three main flavonoid pigments (cyanidin, pelargonidin and maritimein) were detected in COP showing photo-energy conversion efficiencies of 1.43%, 0.87% and 0.60%, respectively. The molecular geometries, electronic structures, optical absorption spectra and proton affinity of these molecules were investigated with DFT/TDDFT. All three molecules displayed π→π * transition dominant in HOMO→LUMO transition. The anchoring groups onto TiO 2 surface were deduced from combined experimental and calculated data. All the constituents of COP are potential sensitizers for DSSC.

We report results of computational study of a newly designed cyanidin based molecular structure, P02, as efficient sensitizers for dye sensitized solar cells (DSSCs). To design this P02, widely used promising natural dye sensitizer cyanidin [1] is combined with α-cyanocinnamic acid and the resultant structure is computationally simulated by using SPARTAN’10 software package [2].The moleculer geometries, electronic structures, absorption spectra and deprotonation enengies of newely designed organic sensitizer are investigated through density functional theory(DFT) and time-dependent density functional theory(TDDFT) approach using GAUSSIAN’09W software package [3]. Furthermore DFT and TDDFT computational calculations are performed on cyanadin too, as reference. The solvation effect in ethanol are included in all calculations.The computational studies on the new dye have shown broadening of the absorption spectra in visible region with significant shifting towards a longer wavelength compared to the cyanidin. Our computational study results indicated that the new dye P02 should exhibit better performance as a sensitizer due to its improved optical properties.

Rice husk ash is a cheap raw material available in abundance in rice-growing countries. It contains around 85–90 % amorphous silica. Rice husk ash, when subjected to a simple chemical precipitation method, will produce nanosilica which can be used for many industrial and technological applications. In this work, we have successfully synthesized nano-sized silica from local rice husk ash and prepared the nanocomposite solid polymer electrolyte, PEO9LiTf:SiO2. The resulting electrolyte has been characterized by X-ray diffraction, differential scanning calorimetry, atomic force microscopy, Fourier transform infrared spectroscopy, and complex impedance spectroscopy. The electrolyte shows about a 12-fold increase in ionic conductivity at room temperature due to the silica filler. In the nanocomposite electrolyte, nanosilica particles obtained from rice husk ash behaved very similarly to the commercial grade nanosilica and had a size distribution in the 25- to 40-nm range. As already suggested by us and by others, the O2− and OH− surface groups in the filler surface interact with the Li+ ions and provide hopping sites for migrating Li+ ions through transient H bonding, creating additional high-conducting pathways. This would contribute to a substantial conductivity enhancement through increased ionic mobility. An additional contribution to conductivity enhancement, particularly at temperatures below 60 °C, appears to come from the increased fraction of the amorphous phase, as evidenced from the reduced crystallite melting temperature and the reduced enthalpy of melting due to the presence of the filler.

Various iodide ion conducting polymer electrolytes have been studied as candidate materials for fabricating photoelectrochemical (PEC) solar cells and energy storage devices. In this study, enhanced ionic conductivity values were obtained for the ionic liquid tetrahexylammonium iodide containing polyethylene oxide (PEO)-based plasticized electrolytes. The analysis of thermal properties revealed the existence of two phases in the electrolyte, and the conductivity measurements showed a marked conductivity enhancement during the melting of the plasticizer-rich phase of the electrolyte. Annealed electrolyte samples showed better conductivity than nonannealed samples, revealing the existence of hysteresis. The optimum conductivity was shown for the electrolytes with PEO:salt= 100:15 mass ratio, and this sample exhibited the minimum glass transition temperature of 72.2 °C. For this optimum PEO to salt ratio, the conductivity of nonannealed electrolyte was 4.4×10−4 S cm−1 and that of the annealed sample was 4.6×10−4 S cm−1 at 30 °C. An all solid PEC solar cell was fabricated using this annealed electrolyte. The short circuit current density (ISC), the open circuit voltage (VOC), and the power conversion efficiency of the cell are 0.63 mA cm−2, 0.76 V, and 0.47% under the irradiation of 600 W m−2 light.

Ionic conductivity, differential scanning calorimetry (DSC), and 1H nuclear magnetic resonance (NMR) measurements have been performed on (PEO)9Mg(ClO4)2 and (PEO)9Mg(ClO4)2 + Al2O3 (neutral, nanoporous) polymer electrolyte systems. It is observed that the conductivity enhances due to the presence of filler up to 15 wt.% and then decreases. The NMR results are consistent with the idea that the conductivity enhancement is mainly due to the increase in chain mobility and ionic mobility of the solid polymer electrolyte caused by increased amorphocity of the electrolyte due to the presence of filler. DSC results also demonstrate that the fraction of the amorphous phase has increased due to the addition of the filler.

ZnO@TiO2 core - shell nanostructures are modified with metal ion dopants to create structures with reduced interfacial charge recombination. ZnO and TiO2 ware doped with Cd and Mg, cauing band-gap changes and increased effective electron lifetime.

Deuterium nuclear magnetic resonance line splitting arising from deformed cis-1,4-poly(butadiene) network, of which the network chain concentration is varied by incorporating protonated free chains of similar kind, is investigated. The results are discussed according to the theoretical framework, introduced by Brereton and Ries,1 which dealt with network vectors which were treated as quenched variables, to show explicitly how they collectively determine the anisotropy in the mean field. The influence of the network chain concentration on the NMR line splitting and molecular weight dependence of Flory interaction parameter χ and the possibility of using the deuterium NMR line splitting to investigate χ parameter of a system are discussed.

Possibility of use of dye extract from skin samples of a seasonal, indigenous fruit from Borneo, namely Canarium odontophyllum, in dye sensitized solar cells (DSSCs) are explored. Three main groups of flavonoid pigments are detected and these pigments exhibit different UV-vis absorption properties, and hence showing different light harvesting capabilities. When applied in DSSCs. The detected pigment constituents of the extract consist of aurone (maritimein), anthocyanidin (pelargonidin) and anthocyanidin (cyanidin derivatives). When tested in DSSC, the highest conversion efficiency of 1.43% is exhibited by cyanidin derivatives, and this is followed by conversion efficiencies of 0.51% and 0.79% for aurone and pelargonidin, respectively. It is shown that individual pigments, like cyanidin derivatives and pelargonidin, exhibit higher power conversion efficiency when compared to that of C.odontophyllum skin pigment mixture (with a conversion efficiency of only 0.68%). The results indicate a possibility of masking effects of the pigments when used as a mixture. The acidification of C.odontophyllum skin pigments with concentrated hydrochloric acid improves the conversion efficiency of the mixture from 0.68% to 0.99%. The discussion in this paper will draw data and observations from the variation in absorption and adsorption properties, the HOMO-LUMO levels, the energy band gaps and the functional group compositions of the detected flavonoids.

Strength and fluctuation of nuclear quadrupolar interaction of filled, partially deuterated cis-1,4 poly(butadiene) networks under deformation are studied by implementing, for the first time, a new NMR method based on nuclear spin correlation of residual dipolar/quadrupolar interactions, demonstrated by Callaghan et. al. [1]. It is shown that this method can probe different dynamics and orientation of polymer chains in filled systems and the results are in good agreement with that reported in literature [17] for the same system but using another NMR methods. Furthermore, the effect of temperature on the quadrupolar interaction of unfilled cis-1,4 poly(butadiene) is studied by using the same method and the results are reported.

A new NMR method, based on nuclear spin correlations of residual dipolar/quadrupolar interactions, demonstrated by Callaghan et. al. (1), is used for the first time to study molecular orientation and dynamics of partially deuterated cis-1,4 poly(butadiene) networks. The polymer networks under deformation and swelling are studied. It is shown that the latter method can probe not only the most dominating orientation and dynamics of the networks but also the sub dynamics of the network due to network inhomogeneities.

Deuterium NMR line shapes of carbon black (N220) filled cis-1,4-poly(butadiene) networks have been examined. The effect of the susceptibility of the filler on the NMR line shape has been considered...

Deuterium nmr has been employed to determine the average orientation of chain segment in poly(butadiene) networks. The nmr spectrum lineshape reveals the orientation distribution of network vectors due to the crosslinks, whereas the observed splitting gives information about the orientation due to segmental interactions. Both the lineshape and the splitting have been fitted simultaneously for a range of deformed poly(butadiene) networks varied in crosslink density and precursor chain length. From the fitting parameters the separate contribution to the average orientation arising from network constraints and interaction are calculated. These are used to estimate the effective molecular weight between topological constraints and the size of the segmental interaction. It could be shown that the latter remains constant as the crosslink density is varied. This is a strong evidence of the recently published theoretical framework.

Deuterium NMR has been employed to determine the average orientation of chain segments in poly(butadiene) networks. It is shown that the free induction decay separates the contribution to the orientation arising from the network constraint to that from chain interactions. The NMR spectrum line shape reveals the orientational distribution of network vectors due to the cross-links, whereas the observed splitting gives information about the orientation due to segmental interactions. Both the line shape and splitting have been fitted simultaneously for a range of deformed poly(butadiene) networks. From the fitting parameters, the separate contributions to the average orientation of the chain segments arising from the network constraint and from the interactions are calculated. These in turn are used to determine the molecular weight between cross-links and the size of the segmental interactions, which we choose to express in terms of the Edwards' screening length. This work is also important to computer model...

We have studied the performance of dye sensitized solar cells sensitized with pigments extracted from the fruit sheath of Nephelium lappaceum (F: Sapindaceae). The pH of the pigment solution used for impregnation was controlled by adding concentrated HCl (50:0.2 v/v). The UV-Vis spectroscopic results revealed that the extract consists of the pigment of Anthocyanin, with an additional absorption peak appearing around 540nm at a lower pH of the pigment solution. Also the band gap of the pigment was reduced by 1eV at low pH conditions. The solar cells fabricated with pigment extracted from the fruit sheath of Nephelium lappaceum showed photo-response with the conversion efficiency of 0.26%, with an open-circuit voltage (VOC) of 453mV, short-circuit current density (ISC) of 1.17mA cm � 2 , and fill factor (ff) of 0.48. The conversion efficiency was significantly enhanced when pH of the pigment solution was lowered by adding concentrated HCl. The conversion efficiency of the dye sensitized solar cells (DSSCs) sensitized after HCl treatment of the pigment was increased to 0.56%, with an open-circuit voltage (VOC )o f 404mV, short-circuit current density (ISC) of 2.71mA cm � 2 , and fill factor (ff) of 0.35. The HOMO level of the pigment at low pH was shown to be shifted towards more positive values with respect to vacuum level, giving rise to an enhanced DSSC efficiency. The overall efficiency enhancement of the low pH pigment was due to the combined effect of increased UV-Vis absorption and efficient adsorption of dye molecules onto the TiO2 semiconductor surface. [DOI: 10.1115/1.4023877]

The precise nature of dye-sensitized solar cell (DSSC) anodes plays a vital role in inter-particle contact, dye absorption, electrolyte diffusion, and distribution of sub conduction band states. This study compares the charge transfer dynamics at the oxide-dye-electrolyte interface in DSSC anodes composed of either nanoparticles (NPs), nanospheres (NSs), or nanorods (NRs). The crystallinity, morphology, visible light and dye absorption on the films were studied by XRD, SEM, and UV-Vis diffuse reflectance spectroscopy while the optoelectronic properties in the DSSC were evaluated by current–voltage, Incident photon to current conversion efficiency, and Electrochemical Impedance Spectroscopy (EIS) measurements. Visible light absorption was highest in NR films while NS films showed the highest light scattering. However, the DSSC with NP films showed the highest power conversion efficiency (PCE) that was attributed to increased dye adsorption amount. The DSSC with NS films had the least PCE but showed the hig...

A Peclet number, Pe, for the drying of colloidal films can be used as a predictor of the uniformity of water concentration in the direction normal to the film. Uniform drying is predicted to occur when Pe < 1, whereas with $\textit{Pe}>1$ , a layer of packed particles is expected to develop above a more dilute layer. Routh and Zimmerman have more recently proposed that the particle concentration gradient between the packed and dilute layers, $d \phi _{p} / d \textit{z} $ , will scale as $\textit{Pe}^{1/2}$ . Here, this scaling relation is tested experimentally with magnetic resonance profiling data obtained from waterborne colloidal films dried under conditions to yield a range of Pe. It is found that $d\phi_{p}/d\textit{z}$ increases with Pe but scales as $\textit{Pe}^{0.8}$ . This disagreement with the prediction can be attributed to an underestimate of Pe when there are greater non-uniformities of drying, because of an unquantified slowing down of the evaporation rate.

A series of high-solids hybrid silicone−acrylic latexes, with varying silicone concentrations and reactivities, was prepared via miniemulsion polymerization. The properties of the resulting coatings have been correlated with their structure and the extent of silicone grafting. The highest silicone incorporation was obtained with silicones containing two reactive vinyl groups polymerized by a semicontinuous method with a delayed addition of neat monomer. It was found that the amount of silicone grafted to the acrylic chains, not the overall total amount in the formulation, was the main factor affecting film properties. Hydrophobicity, water resistance, and thermal stability all increased with the amount of grafted silicone. Coatings that contained high levels of nongrafted silicone displayed separate submicrometer silicone phases and exhibited inferior properties. When silicone was incorporated into the acrylic particles, the total drying time of the coating was shorter, and the water distribution—as deter...