The use of activated coconut shell charcoal (ACSC) was explored as a cost-effective and viable alternative to platinum (Pt) counter electrodes (CE) in CdS quantum dot–sensitized solar cells (QDSSCs). The photovoltaic performances of QDSSCs with newly fabricated ACSC CEs by spraying method and Pt CEs were evaluated using current density–voltage measurements under 100 mWcm−2 light illumination. While the QDSSC with a Pt CE showed an efficiency of 1.26

This study explored the effects of Neodymium-doped graphene quantum dots (NdGQDs) on improving the performance efficiency of TiO2 based dye-sensitized solar cells (DSSCs). By employing in-situ physical assisted mixing, DSSCs with optimized NdGQDs in TiO2 photoanodes showed a power conversion efficiency of 8.76 %, a significant improvement compared to the 6.01 % efficiency of pristine TiO2-based DSSCs under 100 mW cm-2 illumination (AM 1.5). Notably, the short-circuit current density increased by 74 %. HRTEM analysis revealed that the NdGQDs have a size range of approximately 7-9 nm. UV-visible spectroscopy and Mott-Schottky analysis revealed a positive shift in the Fermi level, promoting better electron transfer and increased photo- current density at the expenses of the open circuit voltage. Electrochemical impedance spectroscopy characterization of DSSCs incorporating NdGQD-modified photoanodes revealed a reduction in electron transfer resistance at the photoanode|dye|electrolyte interface, accompanied by an increase in recombination resistance within the device suppressing the electron recombination rate.

Graphene is a potential candidate material to boost efficiency in solar cells. The performance of multilayer TiO2 photoanode-based quasi-solid-state dye-sensitized solar cells (DSSCs) is improved by strategically integrating graphene into the appropriate layer of the photoanode. For this purpose, graphene was synthesized from vein graphite, received directly from the mine site, providing a cost-effective, feasible, and new approach to enhance DSSC efficiency. Raman and XRD spectra confirm the successful exfoliation of graphite, forming graphene. Graphene integration into layers was analyzed using SEM images. The cells were constructed using photosensitized spin-coated TiO2 multilayer photoanode, Pt counter electrode, and binary salt gel polymer electrolyte. Appreciable performance improvement was observed when graphene was added to the fourth layer of the photoanode. The quasi-solid-state DSSC without graphene demonstrated 5.50

Electrochromic devices based on nanofiber membrane gel electrolytes offer several advantages over polymer gel electrolytes. Many advantages, such as high chemical stability, easy handling, less leakage, a wide working temperature range, and a long cycle life, show high compatibility of nanofiber membrane electrolytes in different electrochemical power devices. In this work, we have succeeded in replacing the liquid electrolyte with a nanofiber membrane–based gel electrolyte prepared by the electrospinning method and applied in electrochromic devices (ECD). Polyacrilonitrile (PAN)–based nanofibers were deposited on a spin-coated SnO2 layer, prepared on a fluorine-doped tin oxide (FTO) glass substrate. The thickness of the fiber mat was varied by changing the time of the electrospinning. Gel-type membrane electrolyte was prepared by soaking the nanofiber membrane electrode in the 1 M LiClO4 in propylene corbonate (PC) solution. TiO2 electrochromic electrode was prepared by the “doctor blade” method. ECDs were fabricated with the configuration of FTO glass/TiO2/PAN-based nanofiber membrane gel polymer electrolyte/SnO2/FTO glass by sandwiching the two electrodes. Electrochromic performance of ECDs fabricated with nanofiber membrane gel electrolyte was compared with ECDs fabricated with liquid electrolyte (1 M LiClO4 in PC) and PAN-based conventional gel electrolyte (PC (0.4 g) + ethylene carbonate (EC) (0.4 g) + LiClO4 (0.03 g) + PAN). ECDs with nanofiber membrane gel electrolytes demonstrate a transmittance variation of 33.40

This paper presents a comprehensive study of the optical transmission, photoconductivity, and morphology of CdS thin films deposited via the chemical bath deposition (CBD) method. The films deposited for 60 min exhibit an optical energy band gap value of 2.42 eV and the highest optical transmission of 75 % in the wavelength range of 500-900 nm. For these films, the transmission electron microscopy imaging shows a distribution of particle sizes around 10 nm. The wavelength dependence of the photoconductivity, extracted from photo resistivity data, shows that the maximum photoconductivity occurs at 492 nm wavelength. This corresponds to an electrical energy band gap of 2.52 eV, which is greater than the optically measured energy gap of 2.42 eV. Based on these results, the electron-hole pair binding energy for CdS films is estimated as 100 meV. According to the electrical resistivity vs. temperature measurements, the activation energy is 1.26 eV which agrees with the electrical energy band gap of 2.52 eV. CdS films annealed under nitrogen gas at 200 degrees C for one hour exhibited an energy gap of 2.32 eV. These films displayed a conductivity of 60 x 10(-4) Scm(-1), a carrier concentration of 6.38 x 10(14) cm(-3), and a mobility of 7.46 cm(2) V-1 s(-1). These impressive characteristics suggest the suitability of CBD-grown CdS films annealed at 200 degrees C in nitrogen gas, to be used as the window material in CdS/CdTe thin film solar cells and other optoelectronic applications.

Graphene is a potential candidate material to boost efficiency in solar cells. The performance of multi-layer TiO2 photoanode based quasi-solid-state dye-sensitized solar cells (DSSCs) is improved by strategically integrating graphene into the appropriate layer of the photoanode. For this purpose, graphene was synthesized from vein graphite, received directly from the mine site, providing a cost-effective, feasible and new approach to enhance DSSC efficiency. Raman and XRD spectra confirm the successful exfoliation of graphite, forming graphene. Graphene integration into layers was analyzed using SEM images. The cells were constructed using photosensitized spin-coated TiO2 multilayer photoanode, Pt counter-electrode, and binary salts gel-polymer electrolyte. Appreciable performance improvement was observed when graphene was added to the fourth layer of the photoanode. The quasi-solid-state DSSC without graphene demonstrated 5.50% efficiency, 700 mA open circuit voltage, 11.04 mA cm-2 short circuit current density and 71.2% fill factor under 1000 W m-2 irradiation. In contrast, the DSSC improved by graphene exhibited 6.8% efficiency, 13.4 mA cm-2 short circuit current density, 770 mA open circuit voltage and 66.2% fill factor under 1000 Wm-2 irradiation. Furthermore, the efficiency and fill factor increase were observed when the irradiance decreased. The DSSC exhibited a remarkable efficiency of 9.4% under 67 W m-2 irradiance. Achieving higher efficiency for quasi-soid state configuration without relying on volatile solvent-based electrolytes is another significance of this study. The study uncovers that the strategic incorporation of graphene, synthesized in an economically viable manner, into specific layers of the photoanode significantly enhances the power conversion efficiency in DSSCs.

Dye-sensitized solar cells were fabricated with a polyethylene oxide (PEO)-based quasi-solid (gel) electrolyte consisting of the ionic liquid 1-hexil-3-methylimidazoliym iodide (HMII), and tetrapropyl ammonium iodide (Pr4N+I−) as the two iodide salts with two dissimilar cations. Titanium dioxide powder (TiO2) (P-25) was added to the polymer electrolyte to enhance the iodide ion conductivity further by the nanofiller effect. The electrolyte and the solar cells were characterized by ionic conductivity and impedance measurements, DC polarization test, and current-voltage measurements. The maximum ionic conductivity of 6.95 × 10−3 S cm−1 at 30 °C was exhibited by the electrolyte composition with a 5 wt

CdTe powder samples have been synthesized using a hydrothermal approach, employing cadmium acetate and tellurium dioxides as sources of Cd and Te, respectively. NaBH 4 was utilized as the reducing agent, and double-distilled water was used as the solvent in the synthesis process. The effect of annealing on the synthesized samples was investigated. The samples have been characterized by x-ray powder diffraction, Raman spectroscopy, UV-Vis-NIR spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, and x-ray photoelectron spectroscopy. The electrical properties (current–voltage and capacitance–voltage) of the as-prepared and annealed CdTe pellets were investigated. These findings indicate that annealing can lead to improvements in crystallinity, crystallite size, and electrical conductance. This paper presents a simple, cost-effective, and versatile method for producing significant amounts of CdTe nanostructure powders with properties suitable for use in the fabrication of CdS/CdTe solar cells.

To utilize abundant solar energy, dye-sensitized solar cells (DSSCs) have attracted researchers’ attention due to many reasons, such as low production costs, easy fabrication methods, low toxicity of the materials, and relatively high-power conversion efficiencies. The use of expensive metal-dye complexes, the lack of long-term stability due to the use of liquid electrolytes, and the use of rare and expensive Pt as the CE are the major drawbacks preventing the large-scale production of DSSCs. However, recent studies showed alternative materials can be used to enhance the DSSC performance. The unique properties of graphene make it an ideal additive to improve the functions of all three components of DSSCs. Graphene’s high optical transmittance and electron mobility are suitable to improve transparent conducting substrates and nanostructured wide bandgap semiconductor layers of the photoelectrode. Graphene quantum dots have a wide absorption spectrum and thus can be used as photosensitizers. High catalytic activity, high electrical conductivity, high corrosion resistance, and a larger specific surface area make graphene and its composites suitable for making CEs. In addition, graphene has been used to improve composite electrolytes intended for DSSCs. Considering all these facts, this article reviews the recent developments and applications of graphene-based materials in photoelectrodes, electrolytes and CEs and the possible uses of graphene to improve DSSCs.

Prices of lithium raw materials keep on increasing exponentially due to their heavy consumption for lithium batteries used in portable electronic devices as well as automobiles. Also, the global lithium deposits are very limited. Hence, sodium-ion batteries (SIBs) have been heavily investigated as cheaper alternatives to expensive lithium-ion batteries, mainly due to the abundance of sodium raw materials. However, one of the major bottlenecks faced by the material research community to commercialize SIBs is the poor ionic conductivity of sodium-ion conducting electrolytes at ambient temperature, especially in the solid-state. Very recently, quasi-solid state polymer electrolytes (QSSPEs) have been proposed to overcome this challenge. In this work, a set of QSSPEs have been synthesized by using poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) host polymer and NaBF4 ionic salt dissolved in EC/PC plasticizer/solvent mixture. The highest conducting composition; 6 PVdF-HFP: 14 NaBF4: 40 EC: 40 PC (wt.%); showed an ambient temperature ionic conductivity of 4.1x10-3 S cm-1. The activation energy is almost same for all the sample compositions studied in this work suggesting that the activation process is mainly controlled by EC/PC. DC polarization test on highest conducting electrolyte composition with a configuration of SS/QSSPE/SS revealed that the electrolyte is predominantly ionic conductor with negligible electronic conductivity; a much desired property for a good electrolyte. Linear sweep voltammetric studies confirmed that the electrochemical stability window of the highest conducting electrolyte is about 3.6 V. This highest conducting electrolyte composition is found to be highly suitable for practical applications in sodium batteries.

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) electrospun polymer nanofibre-based quasi-solid or gel electrolytes were successfully fabricated by incorporating a liquid electrolyte within the nanofibre membrane. The dye-sensitized solar cells (DSSCs) fabricated with gel and with liquid electrolyte were characterized by photocurrent–voltage measurements and electrochemical impedance spectroscopy measurements. The maximum efficiency (η) of 6.79% was observed for the DSSC fabricated with optimized nanofibre membrane thickness, corresponding to 4 min of electrospinning time. The optimized PVdF-HFP nanofibre gel electrolyte shows an ionic conductivity of 7.16 × 10−3 S cm–1 at 25°C, while the corresponding liquid electrolyte exhibits an ionic conductivity of 11.69 × 10–3 S cm–1 at the same temperature. The open circuit voltage (Voc), short circuit current density (Jsc) and fill factor were recorded as 801.40 mV, 12.70 mA cm–2, and 66.67%, respectively, at an incident light intensity of 100 mW cm–2 with a 1.5 AM filter. The nanofibre gel electrolyte-based cell showed an efficiency of 6.79%, whereas the efficiency of the conventional liquid electrolyte-based cell was 7.28% under the same conditions. Furthermore, nanofibre gel electrolyte-based cells exhibited better stability, maintaining 85.40% of initial efficiency after 120 h. These results show that the optimized, polymer nanofibre-based gel electrolyte can be used successfully to replace the liquid electrolyte in DSSCs without much loss of efficiency but improving the stability while minimizing most of the drawbacks associated with liquid electrolytes.

We report the growth of CdTe thin films using a wet-chemical electrochemical technique in an aqueous bath. The effect of bath temperature is investigated in detail on the various properties of the sample and the optoelectronic performance of the solar cell devices. A three-electrode technique was employed to deposit the samples at − 0.7 V concerning the Ag/AgCl reference electrode optimized by cyclic voltammetry measurements. The sample annealed at 450 °C for 20 min exhibited a polycrystalline cubic crystal structure of CdTe with an optical energy bandgap of 1.45 eV. The Raman analysis reveals the growth of highly polycrystalline CdTe. All samples were highly compact and well-adherent to the substrate without pinholes. The annealed sample grown at a bath temperature of 50 °C exhibited a large globular grain size of 1 μm. Furthermore, the stoichiometric (50:50) growth of Cd and Te was confirmed using EDAX for the sample grown at a bath temperature of 50 °C. A typical solar cell device, glass/FTO/CdS/CdTe/Au, was measured under dark and illuminated conditions with an input intensity of 100 mW/cm2 and showed a fill factor of 50

This study is about investigating the effect of adding TiO 2 -coated silver nanowires into a tri-layered photoanode of dye-sensitized solar cells (DSSCs) to improve the photovoltaic performance. Face-centred cubic silver nanowires (AgNWs) were synthesized via a rapid, scalable and green pathway method. The average length and diameter of AgNWs were 5 μm and 70 nm, respectively. AgNWs were coated with titanium dioxide (TiO 2 ) using 2-mercaptoethanol as the binder. AgNW@TiO 2 core-shell structure was formed by the hydrothermal method and the average diameter of the coated TiO 2 was observed to be 14 nm. TiO 2 shell showed anatase phase, which was a significant advantage for higher dye absorbance leading to a higher power conversion efficiency (PCE). The PCE for a DSSC with single-layered TiO 2 photoanode increased from 6.70 to 8.87% due to AgNW@TiO 2 core-shell structured photoanode, reflecting a 32.3% enhancement. The PCE for a DSSC with tri-layered AgNWs@TiO 2 core-shell structured photoanode was 10.5% showing an impressive enhancement of 49.6% compared to the DSSC with a pure tri-layered TiO 2 photoanode. TiO 2 shell appears to act as a protective shell around AgNWs by both resisting redox chemical corrosion of Ag by iodide ions in the electrolyte and increasing the thermal stability of AgNWs against annealing at high temperatures. Further, TiO 2 -coated AgNWs facilitate increased photoelectron generation by plasmonic effect, reduce the recombination and enhance the electron lifetime while providing a direct pathway for excited electrons leading to a significant improvement in the PCE of DSSC.

Diatom frustules are incorporated into multilayer photoelectrodes intending to enhance efficiency in dyesensitized solar cells utilizing their light interaction properties. A specific, but ubiquitous in all oceans, pennate-type diatom frustules were used to form the composite layers. Single, double, and triple-layer photoelectrodes were constructed with pure TiO2 (control measurements) as well as with a TiO2/diatom frustule composite. The electrodes were prepared using TiO2 nanoparticles of two sizes (13 and 21 nm) and were analyzed using UV visible absorption and XRD spectra. The morphology of frustules and electrodes were analyzed using scanning electron microscopy. The performance for each photoanode configuration was measured by assembling photoelectrochemical solar cells fabricated with a Pt counter electrode and a gel polymer electrolyte that excludes volatile solvents. The efficiency of the control cell is 3.37%. After replacing the topmost TiO2 layer with a TiO2/diatom frustule composite layer, efficiency increases to 6.78%. This is an impressive efficiency enhancement of 101%. The short circuit current density of frustule-incorporated threelayer cells is 18.1 mA cm-1 while for the control cell it is 8.98 mA cm-1. The enhanced efficiency of cells made with TiO2/diatom frustule composite electrodes and a polyethylene oxide-based gel polymer electrolyte can be attributed to the improved light absorption by the photoanode due to optical scattering and light-trapping effects caused by the presence of diatom frustules. Frustules also can assist in enhancing dye adsorption by increasing the effective specific surface area of the composite photoelectrode due to their nanoporous structure.

Temperature dependence of ionic conductivity of three different compositions of the Mg(BH4)2:polyethylene oxide (PEO):propylene carbonate (PC) polymer gel electrolyte with Mg(BH4)2:PEO molar ratios of 1:8, 1:10, and 1:12 was studied. The composition with Mg(BH4)2:PEO = 1:10 exhibited the highest ionic conductivity of 7.60 × 10−6 S cm−1 at 30 °C. The effect of TiO2 nanofiller on ionic conductivity enhancement was studied for Mg(BH4)2:PEO:PC:TiO2 polymer gel electrolyte by varying the TiO2 weight ratio from 0 to 12.5 wt.

The effect of the thickness of a multilayer TiO 2 photoanode on the performance of a dye-sensitized solar cell (DSC) made with a polyethylene oxide-based gel polymer electrolyte containing ternary iodides and performance enhancer 4-tert-butylpyridine is studied. Multilayer photoanodes consisting of up to seven layers of TiO 2 nano-particles (13 nm and 21 nm) are prepared by spin coating of successive layers. XRD results confirm the predominant presence of the anatase phase of TiO 2 in the multilayer structure after sintering. The SEM images reveal the formation of a single TiO 2 film upon sintering due to merging of individually deposited layers. The photocurrent density ( J SC ) and the efficiency increase with the number of TiO 2 layers exhibiting the maximum efficiency and J SC of 5.5% and 12.5 mA cm −2 , respectively, for the 5-layered electrode of total thickness 4.0 µm with a 9.66 × 10 –8 mol cm −2 surface dye concentration. The present study introduces a method of determining the rate of effective photoelectron generation and the average time gap between two successive photon absorptions where the respective results are 1.34 molecule −1 s −1 and 0.74 s for the most efficient cell studied in this work.

Co-sensitization of TiO2 photoanodes in solar cells with Ruthenium dye and quantum dots offer better photovoltaic performance compared to the sensitization by the dye only. In the present study, TiO2 nanostructured photoanode was co-sensitized with CdS quantum dots and N719 dye. CdS quantum dots were deposited using successive ionic layer adsorption and reaction (SILAR). A suitable thin ZnS interfacial layer has been introduced between two sensitizers to prevent the corrosion of CdS quantum dots by the iodide-based liquid electrolyte. In order to get the highest efficiency, the number of SILAR cycles for CdS quantum dot deposition has been optimized. A power conversion efficiency of 6.79% with short-circuit current density of 15.55 mA cm-2 and open circuit voltage of 764.5 mV have been obtained for the co-sensitized solar cell made with TiO2/CdS/ZnS/N719 co-sensitized photoanode under the illumination of 100 mW cm-2 with AM 1.5 spectral filter. Efficiency and short-circuit current density of the solar cell have been enhanced by 11.31% and 6.58% respectively due to the co-sensitization. The optimized co-sensitized solar cell shows a higher incident photon to current conversion efficiency and a reduced electron recombination compared to the solar cell with dye-sensitized photoanode. Higher recombination resistance and longer electron lifetime of the solar cell with CdS/ZnS/N719 co-sensitized TiO2 photoanode have contributed to the increased short circuit current and open circuit voltage leading to the enhanced efficiency of 6.79% which is among the highest for a co-sensitized dye sensitized solar cell.

Fabrication of efficient CdS quantum dot sensitized solar cell with a novel stable counter electrode based on a thin film of SnO2 is revealed. The film was characterized by using Scanning Electron Microscopy (SEM), High -Resolution Tunneling Microscopy, X-ray diffraction (XRD) and UV-Visible spectroscopic techniques. Photovol-taic performances and Electrochemical Impedance Spectroscopic techniques (EIS) were performed on FTO/TiO2/ CdS/polysulfide/SnO2/FTO device under the light illumination of 100 mW cm(-2) and comparison was done with the conventional Pt counter electrode. Impressive 43 % efficiency enhancement in these solar cells was achieved compared with the Pt based devices. Porous thick nanostructure of SnO2 with crystal defects such as oxygen vacancies and Sn vacancies arising from lattice structures as confirmed by SEM, Raman and, XRD spectroscopy could be some of the reasons for this enhancement. Excellent photo enhanced electrocatalytic activity against the polysulfide electrolyte is confirmed by EIS and Cyclic Voltammetry studies.

Hummer's method, in which potassium permanganate (KMnO4) acts as the oxidant and concentrated sulfuric acid (H2SO4) serves as the intercalator is commonly used to prepare Graphene Oxide (GO). The amount of the intercalator, oxidant, and graphite are important factors that affect the properties and structure of graphene oxide. In this work, a detailed investigation is carried out to optimize the mechanism of Hummer's method in order to get the maximum yield of GO and reduced graphene oxide (rGO). XRD, SEM, TEM, FT-IR, TGA, Raman spectroscopy, and UV -Visible spectroscopy are used for characterization. XRD results of optimized samples (Opt -3 -GO and Opt-3-rGO) clearly showed that the value of interlayer spacing is increased due to increasing the amount of oxidant and intercalator. SEM and TEM results revealed that the Opt-3-rGO was highly wrinkled nanosheets as compared to the Opt -3 -GO. The FT-IR results showed that the double amount of oxidant and intercalator had an effect on the functional groups in the structure of Opt -3 -GO and Opt-3-rGO. TGA results indicated that Opt-3-rGO has higher thermal stability as compared to Opt -3 -GO due to the lower defect density. The ratio of intensities of D and G bands (ID/IG) increased for Opt-3-rGO as compared to Opt -3 -GO. UV-Vis spectra of Opt -3 -GO showed a maximum absorption peak at 237 nm attributable to pi-pi* transition of the atomic C -C bonds. The prepared samples have their use in different applications such as electrode materials for batteries, capacitors, and solar cells.