Rare earth doped metal tungstate (Y1.86WO6: (Eu0.14)3+) of submicron sized particles were prepared via low-temperature combustion method. This was later used as down converter and light scattering ...material in dye-sensitized solar cells (DSSCs). Morphological, compositional and optical properties were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), UV-Visible diffuse reflectance spectroscopy (DRS) and Photoluminescence (PL) spectroscopy. These particles were added with other constituents in the process of fabricating N719 or N749 stained photoanode for DSSCs. Devices fabricated using 2 wt% phosphor constituent showed an appreciable enhancement in short-circuit current density (Jsc) as well as higher power conversion efficiency (PCE) compared to devices without phosphor content. The observed enhancement in efficiency is due to downconversion luminescence and light scattering effects arising from these phosphors particles. Further compared with the N719 based device, the enhancement in PCE for N749 based device is 59%. The significant enhancement in PCE is mainly attributed to the optical wavelength matching between the emission of phosphor and the absorbance of the N749 sensitizer. Thus our work demonstrates how the phosphor material dually improves the DSSC efficiencies.
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•Low-temperature combustion route adopted to prepare Y1.86WO6: (Eu0.14)3+ phosphor.•DSSC devices fabricated using phosphor doped TiO2 coated FTO plates as photoanodes.•33% efficiency enhancement achieved when 2 wt% dopant was incorporate with TiO2.•Luminescence conversion effect Vs light scattering effect was analyzed in detail.
The vertically aligned TiO2 Nanotubes (TiNTs) extracts electrons from an absorber and also helps in its transport in perovskite and dye sensitized solar cells (DSSCs) solar cells. Thus electron ...transporting layer plays a very important role in photon to electron conversion. Electrochemical anodization is been used widely to grow TiNTs for solar cell applications; due to its low cost, flexibility to vary pore diameter and tube length. We observed that, TiNTs maintained its tubular array only for a set time period. On increasing the growth time they begin to take the form of nanocrystals with {001} facets. Formation of these titanium nanocrystals (TiNcs) was clearly observed through field emission scanning electron microscope (FESEM) and Transmission electron microscopy (TEM). Thus TiO2 nanostructures can be tuned by varying anodization time. More importantly, optimization of the reaction process led to the growth of more orderly, crystalline anatase TiNTs/TiNcs over Ti metal foil substrate. The crystal structure and surface morphology of the prepared thin film samples were studied using X-ray diffraction (XRD) technique and scanning and transmission electron microscopes (TEM). XRD confirmed the anatase phase of as grown TiO2 with (101) as major intensity preferred orientation. Lattice parameters calculated were found to be a= 3.77-to-3.82 and c= 9.42-to-9.58 for grown TiO2.
In this study we used photosynthetic pigments extracted from spinach and purple cabbage for their potential application in dye sensitized solar cells (DSSC). Pigments were extracted by dissolving ...small amounts of each one of these plant products in methanol and distilled water. The extraction was also done at two different temperatures (70° C and 80° C respectively). This was to assess for the solvent that promotes better extraction of the pigments. A parallel study was also carried out using a mixture of both these dyes in 1:1 ratio. Good absorption, about 60% to 80% was obtained for spinach pigments diluted in methanol in the visible range between 400-480nm, and between 9% to 15% for purple cabbage pigments in the wavelength range between 480-630 nm when extracted using distilled water at 80°C. In contrast, the diluted mixture in methanol shows good absorption of 20% and 32% for wavelengths in the range 400-480nm. Solar cells sensitized using these natural dyes were studied for their photovoltaic properties by measuring current-voltage behavior. Efficiencies ranging from 0.011% to 0.0719% were observed. Mixture of spinach & purple cabbage pigments extracted using methanol was found to have the highest efficiency of 0.0719%.
New donor molecules with low ionization potential have been theoretically designed by replacing the benzene moieties in triphenylamine (TPA) with thiophene as well as furan. The designed new donors ...also exhibited planar structure, making an angle of 120° around the nitrogen atom that results in resonance effects through π-bonds of aryl rings. New sensitizers have been theoretically studied using DFT and TD-DFT by adopting these designed donors. UV–Vis absorption spectra, light harvesting ability (LHE) and electron injection ability (ΔGinject) of the designed sensitizers have been calculated by taking L0 as reference. Orbital overlapping between donor and acceptor facilitates intra-molecular charge transfer, thereby increasing the interfacial electron injection from the sensitizer to the semiconductor nanoparticles. Our theoretical results demonstrate that sensitizers DTPA-AA and DFPA-AA have broader absorption and lower ΔGinject respectively compare to L0, this opens a new way for designing sensitizers for dye sensitized solar cells (DSSCs). All the dyes designed were found to be good light harvesters.
New donor molecules with low ionization potential have been designed and studied theoretically by substituting the benzene moieties in triphenylamine (TPA) with thiophene as well as furan and new sensitizers such as DXPA-AA and TXA-AA have been explored by adopting these designed donors for dye-sensitized solar cells (DSSCs). Our theoretical studies demonstrate that partial replacement of benzene moieties in TPA results in a good sensitizers. Display omitted
•New donor molecules with low ionization potential using thiophene and furan have been theoretically designed.•New sensitizers have been designed using these molecules as donors and were studied by DFT and TD-DFT methods.•UV-Vis, LHE and ΔGinject of the designed DTPA-AA and DFPA-AA sensitizers showed good parameters than L0.
Carbazole and triphenylamine, are two well-known hole transporting units that are attached to electron transporting unit 4,5-diazafluorene in a fascinating way to bring out non-planar configuration ...of a molecule. The synthesized compound exhibits good thermal stability (T
> 515 °C) and high glass transition temperature (T
, 191 °C). Optical bandgap (E
) obtained from solid state absorption spectra was calculated to be 2.93 eV. Solid state photoluminescence spectra displays the emission maxima at 473 nm. The emission characteristics of the compound observed in solvents of different polarity confirms the existence of intramolecular charge transfer in their excited state. Density functional theory studies reveal that HOMO and HOMO-1 localized on triphenylamine is spatially separated from LUMO of 4,5-diazafluorene, which manifest its bipolar character. The realization of long lived charge separated state upon photo-excitation from time resolved photoluminescence studies ascertains the charge transfer from triphenylamine to 4,5-diazafluorene. The experimental and theoretical analysis of the compound proved it to be a promising candidate for the fabrication of OLED devices.
In this work, we report the synthesis of TiO2 photoelectrodes sensitized with different natural organic dyes extracted (using methanol) from spinach, raspberry and passion fruit for their application ...in Dye-Sensitized Solar Cells (DSSC). The effects of Lead Sulfide (PbS) NanoParticles (NPs) doping on the sensitized TiO2 photoelectrodes photovoltaic performance were mainly studied. Good absorption in the visible range (400–700 nm) was observed for natural dyes extracted from spinach and raspberry, observing characteristic peaks associated with chlorophylls, β-carotenes and phycoerythrin pigments. On the other hand, natural dye synthesized from passion fruit showed a poor absorption in this range concerning the previous mentioned sources. Cells using spinach and raspberry based dyes generally showed good Fill Factors (FF) higher than 55%, observing depreciable or negative influence of the PbS doping. Open-Circuit voltages (Voc), Short-Circuit current densities (Jsc) and Power Conversion Efficiencies (PCE) in the range of 0.35–0.55 V, 0.01–0.12 mA/cm2 and 0.002–0.03 % were respectively estimated.
•Natural organic dyes were synthesized from spinach, raspberry and passion fruit.•Spinach and raspberry dyes showed considerable optical absorption in visible range.•DSSCs presented high fill factors (>55 %) by using spinach and raspberry dyes.•PbS-NPs doping depreciably or negatively affected the photovoltaic performance.•Results suggest possible incompatibilities between PbS-NPs and natural dyes.
Two bipolar fluorophores, namely CEDF and CPDF containing carbazole moiety as electron donor and 4,5-diazafluorene unit as electron acceptor were synthesized and characterized. Carbazole units ...attached to C-2, C-7 and C-9 positions of 4,5-dizafluorene posing an ideal model of donor-acceptor systems to investigate their photo-physical properties for application in organic light emitting diode (OLED) devices. Both compounds possess high thermal stabilities (Td > 450 °C) and high glass transition temperature (Tg), 182 °C and 180 °C for CEDF and CPDF respectively. These compounds revealed solvent polarity dependent emission spectra which confirm the excited state undergoes intramolecular charge-transfer (ICT) process in the molecule. Solid state emission is observed in the blue region at 447 nm for both the compounds. CPDF exhibit higher photoluminescence quantum yield (0.76) than CEDF (0.55) featuring its highly emissive ICT excited state. Using the oxidation and reduction potentials determined from cyclic voltammetry analysis, estimates of both the ionization potentials and electron affinity of the compounds are obtained under the same experimental conditions. HOMO and LUMO energy levels, singlet (ES) and triplet (ET) energy levels of the compounds were obtained through density functional theory (DFT) and time-dependent DFT calculations. A transient photoluminescence curve with a prompt fluorescent component gives an average lifetime of about 5.7 ns for both the compounds. These studies and the convenient synthetic methodologies starting from the 4,5-diazafluorene, make these molecules attractive opto-electronic materials for their application in OLED devices.
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•Two novel Carbazole-diazafluorene based fluorophores were synthesized.•Thermal analysis reveals high Td (>450 °C) and high Tg (~180 °C) of fluorophores.•These two fluorophores exhibited blue emission (447 nm) in solid state.•Positive solvatochromic effect confirms the intramolecular charge transfer excited state.
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•ZnO QDs were synthesized through simple solution process.•ZnO QDs were homogeneously distributed on MWCNT surfaces were identified using TEM analysis.•The electro catalytic activity ...tested towards the oxidation of Glucose by cyclic voltammetry.•The non-enzymatic glucose sensor showed a low detection limit of 0.1 µM.•The MWCNT/ZnO QDS/GC to be an effective sensor for direct determination of glucose in human urine sample.•The photocurrent performance of ZnO/MWCNT composite also studied.
Hybrid nanocomposites consisting of carbon nanotubes (CNT)/nanomaterial heterostructure play a key part in the excellent performance of nano-devices by coupling different functionalities. In this study, a glucose sensor was fabricated by immobilizing zinc oxide quantum dots (ZnO QDs) on multiwall carbon nanotubes (MWCNTs) nanocomposites using ultrasonication in an ease and economical method. ZnO QDs with ~ 3–8 nm diameters were grown and anchored on the surface of MWCNTs. These nanocomposites were characterized using different spectroscopy and microscopy techniques. XRD reveals the wurtzite structure of ZnO. TEM confirmed that ZnO QDs were anchored onto MWCNTs. The synthesized nanocomposites were applied as a sensor for electrochemical detection of glucose and as a photoelectric effect for photoelectric current measurements. The electrochemical properties of the MWCNT/ZnO QDs nanocomposite were enhanced significantly for glucose sensing when compared to pristine ZnO and MWCNTs. Results showed that ZnO QDs anchored over MWCNTs have a sensitivity of 9.36 µA µM−1 with repeatable results. The detection limit was found to be 0.208 µM. By applying nanocomposites on the sensor, the linear range could be extended from 0.1 to 2.5 µM, which increases the response time to less than 3 s. Experimental results also indicate that the sensor response is unaffected by the common interference agents during glucose-sensing such as sucrose, ascorbic acid, dopamine and uric acid. The proposed sensor was successfully employed to detect glucose levels in human urine samples with satisfactory outcomes.
Dye-sensitized solar cell (DSSC) is considered as an excellent indoor photovoltaic (PV) technology because it shows better performance even in scattered indoor light, low cost, high flexibility, ...semi-transparency in nature and availability of variety of colors. Counter Electrode (CE) is one of a crucial component in DSSC as it collects electrons from the external circuit and also act as a catalyzer towards iodide/triiodide (I−/I3−) redox couple in the electrolyte. Platinum (Pt) noble metal is commonly used as a CE material for designing DSSC. But, due to high cost and corrosion activity towards the I−/I3− reduction process, Pt lost its application. Hence, in order to develop a Pt-free CE, several new materials have been explored to fabricate highly efficient DSSC. In this review, the recent progress of binary and ternary transition metal chalcogenides (TMC) and their composites as an effective CE to replace expensive Pt metal CE in DSSC are discussed.
TiO2/ZnS nanocomposites were synthesized using facile ultra-sonication method. Structural, morphological and optical properties of as-synthesized nanocomposites were investigated. The X-Ray ...diffraction pattern exhibits anatase phase of TiO2 without the influence of ZnS phases in the composites. Morphology of the samples were studied using TEM which confirmed the presence of discrete globular like particles. Optical absorption spectra of the nanocomposites showed an enhancement in UV–Vis region. DSSC were fabricated using the synthesized nanocomposites as a secondary layer grown over FTO/TiO2 photoanode. Amongst the constructed cells TiO2 with 1% ZnS showed the highest efficiency of about 4.1% which is an enhancement of 27.7%, higher than that obtained for pure TiO2.
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•Facile ultra-sonication method was adopted to prepare ZnS/TiO2 nanocomposites.•XRD, Raman and UV–Vis absorption spectra was analysed in detail.•DSSC devices fabricated using nanocomposite as secondary layer.•27% efficiency enhancement achieved when 1 wt% ZnS dopant was incorporate with TiO2.
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