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Highly efficient nanocomposite electrolytes were prepared by mixing the montmorillonite (MMT) clay nanofillers and iodide poly(vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) gel electrolytes for the purpose of measuring the performance of quasi-solid-state dye-sensitized solar cells (QS-DSSCs). The impacts of different amounts of MMT nanofillers on the ion diffusivity, conductivity of the polymer gel electrolytes (PGEs), and the photovoltaic performance of the cells using the PGEs were evaluated. The results indicated that the use of 5 wt.% MMT markedly increase the ion diffusivity and conductivity of the PVDF-HFP PGE. The introduction of 5 wt.% nanofillers considerably reduced the Warburg diffusion resistance, which made to the high performance of the QS-DSSCs. Cells utilizing 5 wt.% MMT nanofillers were shown to obtain a power conversion efficiency (PCE) (6.77%) higher than that obtained for cells using pure PGEs and identical to that obtained using liquid electrolytes (LEs) (6.77%). The high PCE was a result of an enhance in the current density in the presence of the 5 wt.% MMT nanofillers. The DSSC efficiency was found to maintain 99.9% of its initial value after 194 h of testing at 60℃ under dark environments. The stability of the DSSC using PGEs with the optimal amount of MMT nanofillers was higher than that for the cells using liquid electrolyte and pure PGE.

High-efficiency, stable bifacial dye-sensitized solar cells (DSSCs) are prepared for application under indoor light conditions. A 3-methoxypropionitrile solvent and cobalt redox couples are utilized to prepare the electrolytes. To obtain the best cell performance, the components of the DSSCs, including electrolytes, photoanodes, and counter electrodes (CEs), are regulated. The experimental results indicate that an electrolyte comprising a Co (II/III) ratio of 0.11/0.025 M, 1.2 M 4-tert-butylpyridine, Y123 dye, a CE with the platinum (Pt) layer thickness of 0.16 nm, and a photoanode with titanium dioxide (TiO2) layer thickness of 10 μm (6 μm main layer and 4 μm scattering layer) are the best conditions under which to achieve a high power conversion efficiency. It is also found that the best cells have high recombination resistance at the photoelectrode/electrolyte interface and low charge transfer resistance at the counter electrode/electrolyte interface, which contributes to, respectively, the high current density and open-circuit voltage of the corresponding cells. This DSSC can achieve efficiencies of 22.66%, 23.48%, and 24.52%, respectively, under T5 light illumination of 201.8, 607.8, and 999.6 lx. For fabrication of bifacial DSSCs with a semitransparent property, photoanodes without the TiO2 scattering layer, as well as an ultrathin Pt film, are utilized. The thicknesses of the TiO2 main layer and Pt film are reregulated. This shows that a Pt film with 0.55 nm thickness has both high transmittance (76.01%) and catalytic activity. By using an 8 μm TiO2 main layer, optimal cell efficiencies of 20.65% and 17.31% can be achieved, respectively, for the front-side and back-side illuminations of 200 lx T5 light. The cells are highly stable during a long-term performance test at both 35 and 50 °C.

High-efficiency and stable quasi-solid-state dye-sensitized solar cells (QS-DSSCs) are fabricated using printable polymer gel electrolytes for application under room light conditions. The printable electrolytes are prepared based on 3-methoxypropionitrile liquid electrolytes containing iodide/triiodide redox mediator, polyethylene oxide/polyvinylidene fluoride gelator, and titanium dioxide nanofillers. To obtain the optimal performance of the DSSCs, the composition of the printable electrolytes and the thickness of the photoelectrode are regulated. The results show that the polymers composition has little effect on the conversion efficiency of the QS-DSSCs under ambient-light conditions. However, the iodine concentration and the thickness of the titanium dioxide film are important parameters. The experimental results indicate that the printable electrolyte containing 0.01 M iodine, and a titanium dioxide photoelectrode with the thickness of 4 µm main layer and 4 µm scattering layer are the optimal condition to obtain high cell efficiencies. It also shows that the best QS-DSSCs have high recombination resistance and high incident photon to current efficiency values, which contribute, respectively, to the high open circuit voltage and the current density of the corresponding cells. Therefore, the cells can achieve efficiencies of 15.39% and 20.63% under 200 and 600 lx illuminance, respectively. These efficiencies are almost similar to the conversion efficiencies of the corresponding liquid-state DSSC. By applying this printable electrolyte to a sub-module cell, an energy conversion efficiency of 12.23% is achieved under 200 lx illuminance. The study of long-term stability shows that the efficiency of the QS-DSSC can retain 97% of its initial performance after 1000 h testing under 200 lx illuminance, exhibiting high stability of the cells.

Highly efficient quasi-solid-state dye-sensitized solar cells (QS-DSSCs) are fabricated using nanocomposite gel electrolytes and applied under room light conditions (200 lx). To obtain high energy conversion efficiency in QS-DSSCs, the important components of the DSSC are systematically optimized based on their performance in liquid-state DSSCs. It shows that the liquid cell using the 3-methoxypropionitrile-based cobalt electrolyte has higher efficiency (18.91%) than the cell using the acetonitrile-based electrolyte (17.82%) under 200 lx illumination due to the higher charge recombination resistance at the photoelectrode/electrolyte interface for the 3-methoxypropionitrile system. Poly(vinylidene fluoride-co-hexafluoropropylene) is utilized as the gelator of the liquid electrolytes to prepare polymer gel electrolytes. Furthermore, to improve the performance of the QS-DSSCs, different metal oxide nanoparticles are introduced as nanofillers of the polymer gel electrolytes. It shows that the zinc oxide nanof...

The behavior of ethanol oxidation reaction on composite electrodes prepared by deposition platinum on a gold surface (Pt/Au) were studied by cyclic voltammetry and surface enhanced infrared absorption spectroscopy (SEIRAS) analysis. The results show that the Pt electrode has high oxidation activity and significant poison behavior; on the contrary, the Au electrode demonstrates low activity without a poison peak. The SEIRAS analyses reveal that both carbon monoxide (CO) and carbon dioxide (CO

A graphene oxide sponge (GOS) is prepared and utilized as a nanofiller (NF) of an iodide liquid electrolyte for dye-sensitized solar cell (DSSC) application. The concentration effects of the GOS NFs on the conductivity of the electrolyte, and the performance of the DSSCs are studied. The results indicate that the inclusion of GOS NFs markedly enhances the conductivity of the liquid electrolyte. The electrochemical impendence spectroscopy (EIS) analysis shows that the presence of GOS NFs may increase the recombination resistance (Rct) at the photoelectrode/electrolyte interface and, furthermore, decreases the charge transfer resistance at the Pt counter electrode/electrolyte interface (Rpt). Therefore, the current density (Jsc), open circuit potential (Voc), and fill factor (FF) of the DSSCs can be improved by controlling the concentration of GOS NFs. In this study, the DSSC with 0.50 wt% GOS NFs can achieve the highest energy conversion efficiency of 9.44%, which is higher than that obtained for the corresponding cell without GOS NFs (8.84%).

A graphene oxide sponge (GOS) is utilized for the first time as a nanofiller (NF) in printable electrolytes (PEs) based on poly(ethylene oxide) and poly(vinylidene fluoride) for quasi-solid-state dye-sensitized solar cells (QS-DSSCs). The effects of the various concentrations of GOS NFs on the ion diffusivity and conductivity of electrolytes and the performance of the QS-DSSCs are studied. The results show that the presence of GOS NFs significantly increases the diffusivity and conductivity of the PEs. The introduction of 1.5 wt % of GOS NFs decreases the charge-transfer resistance at the Pt-counter electrode/electrolyte interface (Rpt) and increases the recombination resistance at the photoelectrode/electrolyte interface (Rct). QS-DSSC utilizing 1.5 wt % GOS NFs can achieve an energy conversion efficiency (8.78%) higher than that found for their liquid counterpart and other reported polymer gel electrolytes/GO NFs based DSSCs. The high energy conversion efficiency is a consequence of the increase in both...

Electrochemical methodologies including constant current, constant potential and cyclic voltammetry (CV), as well as the sputter coating, are utilized to fabricate the poly(3,4-ethylene dioxythiophene) (PEDOT), platinum (Pt), and their composite films with layer-by-layer (Pt/PEDOT) and homogenous (PEDOT-Pt) structures. These films are utilized as counter electrodes of dye-sensitized solar cells (DSSCs). To achieve high cell efficiencies, the thickness of Pt and PEDOT, as well as the structure of composite films are regulated. The results show that PEDOT/Pt and PEDOT-Pt films demonstrate, respectively, the best and worst cell efficiencies. The X-ray diffraction and X-ray photoelectron spectroscopy analysis indicate that PEDOT and Pt have slight interaction in the PEDOT/Pt film, and the Pt preserves a crystalline structure. On the contrary, the interaction of PEDOT and Pt in the PEDOT-Pt film is high, resulting in an amorphous Pt structure. The crystalline Pt and its interaction with PEDOT are considered to be the main reason resulting in the high efficiencies of the corresponding cells. By applying this PEDOT/Pt counter electrode on DSSCs, the charge transfer at the counter electrode/electrolyte interface is significantly increased, and the cells can achieve efficiencies as high as 8.97% and 15.35%, respectively, under one-sun and room-light (200 lux) conditions.

In this study, highly efficient printable electrolytes (PEs) were prepared for a quasi-solid-state dye-sensitized solar cell (QS-DSSC). A liquid electrolyte based on iodide/triiodide redox couples and 3-methoxypropionitrile (MPN) was utilized to prepare the PEs. Poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) were employed as solidifying agents to optimize the properties of the PEs. Moreover, TiO2 nanofillers (NFs) were added to the PEs to enhance the performance of the DSSCs. The results indicate that a PE based on a PEO/PMMA ratio of 7/3 was optimal for efficient printing. The energy conversion efficiency of the DSSC achieved by using this PE was 8.48%, which was higher than the efficiencies of the cell using only PEO PE (7.63%) and liquid-cells (8.32%). This was mainly due to the increase in the electrolyte conductivity and charge transfer resistance at the photoelectrode/electrolyte interface of the DSSC. The presence of 10 wt% TiO2 NFs in the PEs increased the efficiency of the QS-DSSC to 9.12%. The sub-module cell fabricated by using the PE with TiO2 NFs achieved an efficiency of 6.78%. The PE based DSSC exhibited stable long-term efficiency during thermal aging at 60 °C.

Dye-sensitized solar cells (DSSCs) are a promising alternative for conventional silicon solar cells in terms of high energy conversion efficiency and low production cost. However, liquid-state DSSCs exhibit poor long-term stability since volatile liquid electrolytes are utilized. An effective, simple approach to improving the stability as well as the photovoltaic performance of DSSCs, is by replacing liquid electrolytes with nanocomposite electrolytes. This paper reviews various state-of-the-art nanocomposite electrolytes in view of their physical and electrochemical properties for application in DSSCs. This review mainly focuses on various types of inorganic materials such as clays, metal oxides, metal nitrides, metal carbides, metal sulfides and carbonaceous materials as nanofillers (NFs) in nanocomposite electrolytes. The influence of the sizes, shapes, and surface functional groups of these NFs on the properties of the nanocomposite electrolytes are described. The working mechanism of the DSSCs based on the interactions of these NFs with the electrolytes are presented. The long-term stability of the DSSCs using nanocomposite electrolytes at different temperatures is reviewed. In addition, the methods used to evaluate the mechanical, electrochemical, thermal and long-term stability of the electrodes, electrolytes, and DSSCs are summarized.

Low-cost counter electrodes for dye-sensitized solar cells (DSSCs) are prepared using platinum/carbon black (Pt/CB) composites via a spin-coating process. Ethyl cellulose (EC) is used as a binder to regulate the viscosity of the Pt/CB composites to facilitate the spin-coating process. The ratio of Pt to CB is ca. 1:3. The effects of film composition (Pt/CB:EC = 30:15, 30:4) and number of coating layers on the electrochemical properties of the Pt/CB electrodes and the performance of the corresponding DSSCs are studied. The results show that Pt/CB films with the lower concentration of EC (Pt/CB:EC = 30:4) exhibit high electrochemical activity, low charge transfer resistance, and good DSSC performance. These results are attributed to the lower loading of EC, which facilitates the charge transfer of the electrodes. DSSCs using these Pt/CB composite counter electrodes with lower loading of EC achieve a high conversion efficiency (8.06%) comparable to that of cells using Pt.

In the literature, so far, in-situ chemical cross-linking methods have been utilized for the preparation of Al2O3 or ZnO-composite polymer gel electrolytes (PGEs). Such PGEs have shown poor performance in quasi-solid-state dye-sensitized solar cells (QS-DSSCs) under one-sun conditions. Moreover, the QS-DSSCs using ZnO-PGEs had higher open-circuit voltages (Voc) than the cell using Al2O3-PGEs; but their conversion efficiencies are much lower. To solve this problem, for the first time, composite printable electrolytes (CPEs) are fabricated by dispersion Al2O3 and ZnO nanofillers (NFs) in the quasi-solid-state electrolytes. The electrochemical properties of the CPEs and their effects on the QS-DSSCs performance are systematically studied and compared. The results show that the diffusion coefficients of ions in Al2O3 CPEs are much higher than in ZnO CPEs. However, the introduction of ZnO NFs significantly decreases the charge recombination at the photoelectrode/electrolyte interface than do by the Al2O3. Therefore, the QS-DSSCs using Al2O3 CPE and ZnO CPE have, respectively, higher current density and higher Voc; and the highest efficiencies achieved are 8.73% and 7.59%. These efficiencies are significantly higher than those reported for the QS-DSSC PGEs using the two NFs. The mechanisms of the two NFs are proposed by analysis the iodide ions on the two NFs using X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy.

Propionitrile (PPN) solvent based iodide/triiodide liquid-electrolyte is utilized to prepare highly efficient poly (vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) polymer gel electrolytes (PGEs) of dye-sensitized solar cells, aiming at improving the energy conversion efficiency as well as the stability of gel-state DSSCs. The concentrations effect of the PVdF-HFP on the properties of PGEs and the performance of the corresponding cells are studied. The results show that the in-situ gelation is performed for the PVdF-HFP concentration range of 8–18% at room temperature. However, increasing the concentration of polymer in the PGEs triggers a decrease in the diffusivity and conductivity of the PGEs, but an increase in the phase transition temperature of the PGEs. A high phase transition temperature is obtained for the PGEs with 18 wt% PVdF-HFP, which increase the long-term stability of the gel-state DSSC. By using the 18 wt% PVdF-HFP in the presence of 5 wt% TiO2 nanofillers (NFs), gel-state cells with an efficiency of 8.38% can be obtained, which is higher than that achieved by liquid-state cells (7.55%). After 1000 h test at room temperature (RT) and 50 °C, the cell can retain 96% and 82%, respectively, of its initial efficiency.

Polymer gel electrolytes (PGEs) of cobalt redox system are prepared for dye sensitized solar cell (DSSC) applications. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) is used as a gelator of an acetonitrile (ACN) liquid electrolyte containing tris(2,2'-bipyridine)cobalt(II/III) redox couple. Titanium dioxide (TiO2) and titanium carbide (TiC) nanoparticles are utilized as nanofillers (NFs) of this PGE, and the effects of the two NFs on the conductivity of the PGEs, charge-transfer resistances at the electrode/PGE interface, and the performance of the gel-state DSSCs are studied and compared. The results show that the presence of TiC NFs significantly increases the conductivity of the PGE and decreases the charge-transfer resistance at the Pt counter-electrode (CE)/PGE interface. Therefore, the gel-state DSSC utilizing TiC NFs can achieve a conversion efficiency (6.29%) comparable to its liquid counterpart (6.30%), and, furthermore, the cell efficiency can retain 94% of its initial value after a 1000 h stability test at 50 °C. On the contrary, introduction of TiO2 NFs in the PGE causes a decrease of cell performances. It shows that the presence of TiO2 NFs increases the charge-transfer resistance at the Pt CE/PGE interface, induces the charge recombination at the photoanode/PGE interface, and, furthermore, causes a dye desorption in a long-term-stability test. These results are different from those reported for the iodide redox system and are ascribed to a specific attractive interaction between TiO2 and cobalt redox ions.

High-performance printable electrolytes (PEs) containing Co+2/Co+3 or I−/I3− redox-couple are prepared to fabricate quasi-solid-state (QS) dye-sensitized solar cells (QS-DSSCs) for room light environment applications. Polyethylene oxide (PEO) and poly(methyl methacrylate) (PMMA) are utilized to prepare PEs. Various parameters are regulated to obtain the optimal power conversion efficiencies (PCEs). For the I−/I3− system, the QS-DSSCs using PEO and PEO/PMMA PEs achieve nearly identical PCEs (16.32% and 16.40%, respectively) under the optimal conditions. However, the PCEs obtained for the Co+2/Co+3 system are markedly higher and the cell using PEO PE has a higher PCE (21.06%) than that using PEO/PMMA (18.14%). This difference is ascribed to the different composition of Li+ and Co+3 around the photoelectrode. The presence of Li+ around the interface will repel Co+3 away from the interface, decreasing the recombination of excited electrons to Co+3. According to the molecular structure, PMMA has more lone pair electrons to coordinate with Li+ ions, which will decrease the concentration of free Li+ more significantly than does by PEO. Therefore, the presence of PMMA will decrease and increase, respectively, the Li+ and Co+3 concentrations at the photoelectrode/electrolyte interface, resulting in more significant recombination of electrons to the Co+3. Consequently, the PCE of the PEO/PMMA cell is lower than that of the PEO cell. This effect doesn’t occur in I−/I3− system because the concentration variation of negatively charged ions did not affect significantly the electrons recombination at the interfacial. By using this cobalt PE, a bifacial QS-DSSC can achieve PCEs of 17.22% and 14.25%, respectively, under front-side and back-side illumination by 200 lx T5 light. A sub-module QS-DSSC using the cobalt PE can attain a PCE of 12.56%.

Phytochemical investigation of the whole plant of Andrographis viscosula has led to the isolation of three new 2'-oxygenated flavonoids, (2R)-5-hydroxy-7,2',3'-trimethoxyflavanone (1), 7,2',5'-trimethoxyflavone (2), 5,7,2',3'-tetramethoxyflavone (3), and eight known flavones, 5,7,2'-trimethoxyflavone (4), 5,7,2',4',5'-pentamethoxyflavone (5), echioidinin (6), 5,2',6'-trihydroxy-7-methoxyflavone (7), 5-hydroxy-7,2'-dimethoxyflavone (8), echioidin (9), echioidinin 5-O-glucoside (10), and 5,2',6'-trihydroxy-7-methoxyflavone 2'-O-glucoside (11). The structures of 1-11 were elucidated by physical and spectral methods, including extensive 2D NMR studies. The presence of 2'-oxygenated flavonoids is apparently restricted to Andrographis species in Acanthaceae. Therefore, 2'-oxygenated flavonoids are regarded as chemotaxonomic markers of Andrographis genus in the Acanthaceae family.

Phytochemical investigation of the whole plant of Andrographis viscosula has led to the isolation of three new 2'-oxygenated flavonoids, (2R)-5-hydroxy-7,2',3'-trimethoxyflavanone (1), 7,2',5'-trimethoxyflavone (2), 5,7,2',3'-tetramethoxyflavone (3), and eight known flavones, 5,7,2'-trimethoxyflavone (4), 5,7,2',4',5'-pentamethoxyflavone (5), echioidinin (6), 5,2',6'-trihydroxy-7-methoxyflavone (7), 5-hydroxy-7,2'-dimethoxyflavone (8), echioidin (9), echioidinin 5-O-glucoside (10), and 5,2',6'-trihydroxy-7-methoxyflavone 2'-O-glucoside (11). The structures of 1-11 were elucidated by physical and spectral methods, including extensive 2D NMR studies. The presence of 2'-oxygenated flavonoids is apparently restricted to Andrographis species in Acanthaceae. Therefore, 2'-oxygenated flavonoids are regarded as chemotaxonomic markers of Andrographis genus in the Acanthaceae family.