Long-term Stability Of Dye-sensitized Solar Cells Research Articles

Integration Device of Super-Capacitors with Dye-Sensitized Solar Cells

Integration Device of Super-Capacitors with Dye-Sensitized Solar Cells

Facile fabrication of ZnCo2S4@MWCNT as Pt-free counter electrode for high performance dye-sensitized solar cells

Substitution of platinum as a counter electrode material in dye-sensitized solar cells (DSSCs) is critical because Pt is rare and expensive. In addition, Pt-based counter electrodes have problems with the long-term stability of DSSCs. Among Pt-free electrocatalysts, composite materials are of great interest because they can be advantageous due to the combined performance of their components. Here, we present a ternary ZnCo2S4 composite grown on multi-walled carbon nanotubes as a Pt-free counter electrode for the reduction of triiodide in DSSCs. The composite ZnCo2S4@MWCNT was synthesized in a simple two-step process: (i) spray coating of a MWCNT dispersion on a FTO glass substrate, followed by (ii) solvothermal growth of the ternary sulfide ZnCo2S4 on a MWCNT layer. Cyclic voltammetry analyzes showed superior electrocatalytic activity of the composite in the reduction of triiodide compared to Pt. Electrochemical impedance spectroscopy measurements of symmetric dummy cells showed lower charge transfer resistance of ZnCo2S4@MWCNT (RCT = 5.54 Ω × cm2) than the traditional Pt electrocatalyst (7.07 Ω × cm2) in catalyzing the triiodide-to-iodide conversion reaction. The photovoltaic measurements of dye-sensitized solar cells showed an improved conversion efficiency of ZnCo2S4@MWCNT (8.55%) with excellent stability compared to Pt (8.19%).

Effect of nanoporous In2O3 film fabricated on TiO2-In2O3 photoanode for photovoltaic performance via a sparking method

A simple and inexpensive sparking method was used to deposit body-centered cubic In2O3 film on TiO2 photoanode for 30–180 min for dye-sensitized solar cells (DSSCs). The effect of nanoporous In2O3 film on photovoltaic performance was investigated. The efficiency of TiO2-In2O3 photoanode with the sparking time for 120 min was the highest of 3.40 and 8.6% rise in conversion efficiency comparing to the TiO2 photoanode device, due to the increasing in short-circuit current density (Jsc) and electron lifetime (Teff). In this research, Jsc improvement was caused by increasing surface area for adsorbed dye molecules. TiO2-In2O3 photoanode exhibited low resistance of charge diffusion (Rct1) at the interface of the redox electrolyte/Pt counter electrode and/or electrical contact between In2O3 nanoparticles by providing an efficient pathway for photogenerated electrons in the DSSCs. Furthermore, the long-term stability of DSSCs showed that TiO2-In2O3 photoanode with 120 min sparking period exhibited the highest efficiency comparing with the pure TiO2 photoanode.

Interfacial Effects in Solid-Liquid Electrolytes for Improved Stability and Performance of Dye-Sensitized Solar Cells.

With the purpose of achieving stable dye-sensitized solar cells (DSSCs) with high efficiency, a new type of soft matter electrolyte is tested in which specific amounts of nanosized silica particles are finely dispersed in short-chained polyethylene glycol dimethylether encompassing an iodide/triiodide redox mediator. This results in a solid-liquid composite having synergistic electrical and favorable mechanical properties. The combination of interfacial effects and particle network formation promotes enhanced ion transport, which directly impacts the short-circuit photocurrent density. Thorough analysis reveals that this newly elaborated class of electrolytes is able to improve, at the same time, the thermal and long-term stability of DSSCs, as well as power conversion efficiency under standard and lower irradiation intensities. Lab-scale devices with champion efficiency exceeding 11% under attenuated sunlight (20 mW cm-2, with a compact TiO2 blocking layer) are obtained, along with impressively stable performance under both thermal stress and light soaking in an indoor environment (>96% performance retention after 2500 h of accelerated aging under full sun alternated with thermal ramps), matching the durability criteria applied to silicon solar cells for outdoor applications. The new findings might foster widespread practical application of DSSCs.

A highly stable and efficient quasi solid state dye sensitized solar cell based on Polymethyl methacrylate (PMMA)/Carbon black (CB) polymer gel electrolyte with improved open circuit voltage

Dye sensitized solar cells (DSSCs) have received significant attention due to their low production cost and easy fabrication process. However, the leakage and volatilization of the liquid organic solvent in the liquid electrolyte affect the long term stability of DSSCs. Therefore, in this present work, to improve the durability of DSSCs, polymethyl methaacrylate (PMMA) based polymer gel electrolyte (PGE) with different weight percent of carbon black (CB) was studied to replace the conventional liquid electrolyte. CB was used to improve the ionic conductivity of the PGE. DSSCs fabricated with the prepared PGEs exhibit very good long term stability in comparison to liquid electrolyte. The optimized DSSC with 0.57 weight percentage of CB in PMMA polymer matrix exhibits the highest photo-conversion efficiency of 5.52±0.03% with short circuit current density (Jsc) value of 12.43±0.04mAcm−2, open circuit voltage (Voc) value of 766.02±0.52mV and fill factor (FF) value of 58.01±0.02%. A significant enhancement of Voc is observed with the employment of the PGE. The impact of the PGE in the enhancement of Voc was studied by analyzing the charge transfer kinetics data at the interface of the photoanode and the PGE. Furthermore, the study of long term stability shows that after 1000h of testing the optimized DSSC (PGE(0.57)) retains the Jsc value at 83% of the initial performance exhibiting very significant long term stability in comparison to the DSSC fabricated with liquid electrolyte.

Preparation of iron diselenide/reduced graphene oxide composite and its application in dyesensitized solar cells

In recent years, dye-sensitized solar cells (DSSCs) have attracted much attention because of their easy fabrication, good flexibility low cost and relatively high efficiency. As a crucial component, the function of counter electrode (CE) is to collect the electrons from external circuits and transfer them to electrolyte by catalyzing the reduction of I3- into I-. Platinum (Pt) is a conventional material of CE in DSSCs due to its high conductivity and outstanding catalytic activity towards the reduction of triiodide (I3-). However, the high cost and low abundance of Pt restrict the commercial application of DSSCs. Moreover, Pt could be dissolved slowly in the I-/I3- redox electrolyte, which will deteriorate the long term stability of DSSCs. Therefore, it is necessary to explore novel material with high conductivity, catalytic activity and stability to replace Pt. In this paper, with Fe(NO3)39H2O and graphene oxide (GO) serving as raw materials and deionized water as the solvent, we synthesize iron diselenide (FeSe2) nanorods (with diameters in a range of about 100-200 nm)/reduced graphene oxide (rGO) composite through a facile hydrothermal method and use the composite as CE material of DSSCs for the first time. The structure and morphology of FeSe2/rGO are characterized by using X-ray diffraction (XRD), Raman spectrum, field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The XRD pattern shows that the FeSe2 is typically orthorhombic phase. The SEM images show that the FeSe2 has a structure of nanonods and can be attached to the surface of rGO closely The surface of FeSe2/rGO composite is rough and exhibits a porous structure. The TEM image shows that the FeSe2 has a high degree of crystallinity and orientation. To evaluate the catalytic activity and conductivity of FeSe2/rGO, we perform cyclic voltammetry (CV) measurements, electrochemical impedance spectroscopy and obtain Tafel polarization curves for FeSe2/rGO electrode and also for Pt, FeSe2 and rGO electrodes for comparison. The results indicate that the CE based on FeSe2/rGO composites has the lowest peak-to-peak voltage separation (E_{pp}) charge transfer resistance (Rct) and series resistance (Rs) in the four different CEs, suggesting that the FeSe2/rGO CE has an excellent electrocatalytic performance for the reduction I3-. The current density-voltage (J-V) curves of DSSCs with different CEs under the illumination of 1 sun (100 mW cm-2) show that the cell with FeSe2/rGO CE has an open-circuit voltage (Voc) of 0.727 V, a short-circuit current (Jsc) of 18.94 mA cm-2, a fill factor (FF) of 0.65 and an excellent power conversion efficiency (PCE) of 8.90%, which is a notable improvement compared with the PCE of the cell with an FeSe2 CE (7.91%) and an rGO CE (5.24%). It can be attributed to the synergetic effects between the FeSe2 nanorods and rGO which eventually improve the PCE of DSSC We also conducte the experiments on the electrochemical stability of FeSe2/rGO CE by sequential CV measurements the result indicates that the FeSe2/rGO composite has a better stability than Pt in I-/I3- electrolyte In summary, we synthesize a novel FeSe2/rGO conductive catalyst. This hybrid material possesses the features of FeSe2 and rGO, exhibiting both highly catalytic activity and high conductivity Therefore, the low-cost and high-performance FeSe2/rGO composite can be a promising CE material to replace Pt in the large-scale industrial production of DSSCs.

Rapid Dye Adsorption via Surface Modification of TiO2 Photoanodes for Dye-Sensitized Solar Cells

A facile method for increasing the reaction rate of dye adsorption, which is the most time-consuming step in the production of dye-sensitized solar cells (DSSCs), was developed. Treatment of a TiO2 photoanode with aqueous nitric acid solution (pH 1) remarkably reduced the reaction time required to anchor a carboxylate anion of the dye onto the TiO2 nanoparticle surface. After optimization of the reaction conditions, the dye adsorption process became 18 times faster than that of the conventional adsorption method. We studied the influence of the nitric acid treatment on the properties of TiO2 nanostructures, binding modes of the dye, and adsorption kinetics, and found that the reaction rate improved via the synergistic effects of the following: (1) electrostatic attraction between the positively charged TiO2 surface and ruthenium anion increases the collision frequency between the adsorbent and the anchoring group of the dye; (2) the weak anchoring affinity of NO3(-) in nitric acid with metal oxides enables the rapid coordination of an anionic dye with the metal oxide; and (3) sufficient acidity of the nitric acid solution effectively increases the positive charge density on the TiO2 surface without degrading or transforming the TiO2 nanostructure. These results demonstrate the developed method is effective for reducing the overall fabrication time without sacrificing the performance and long-term stability of DSSCs.

Photophysical and Electrochemical Properties, and Molecular Structures of Organic Dyes for Dye‐Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) based on organic dyes adsorbed on oxide semiconductor electrodes, such as TiO(2), ZnO, or NiO, which have emerged as a new generation of sustainable photovoltaic devices, have attracted much attention from chemists, physicists, and engineers because of enormous scientific interest in not only their construction and operational principles, but also in their high incident-solar-light-to-electricity conversion efficiency and low cost of production. To develop high-performance DSSCs, it is important to create efficient organic dye sensitizers, which should be optimized for the photophysical and electrochemical properties of the dyes themselves, with molecular structures that provide good light-harvesting features, good electron communication between the dye and semiconductor electrode and between the dye and electrolyte, and to control the molecular orientation and arrangement of the dyes on a semiconductor surface. The aim of this Review is not to make a list of a number of organic dye sensitizers developed so far, but to provide a new direction in the epoch-making molecular design of organic dyes for high photovoltaic performance and long-term stability of DSSCs, based on the accumulated knowledge of their photophysical and electrochemical properties, and molecular structures of the organic dye sensitizers developed so far.

Liquid crystal based electrolyte with light trapping scheme for enhancing photovoltaic performance of quasi-solid-state dye-sensitized solar cells

In this study, nematic liquid crystal, 4-Cyano-4′-n-heptyloxybiphenyl, is introduced into the poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF) based polymeric gel electrolyte for quasi-solid-state dye-sensitized solar cells (DSC), aiming to improve the photovoltaic performance of DSC. The effects of liquid crystal on the electrochemical behavior of I 3 −/ I − and photovoltaic performance, dynamic response as well as long-term stability of DSC are studied in detail. It is found that although the addition of liquid crystal would hinder the charge transport in the electrolyte, it could still fulfill the requirements of the photocurrent for DSC. More important, a significant increase in the photocurrent density for DSC is observed when liquid crystal is introduced into PVDF based polymeric gel electrolyte, resulting in the higher photoelectric conversion efficiency. The large increase in short-circuit photocurrent density could be attributed to the higher light harvesting efficiency, which is caused by the effective formation of light trapping scheme in electrolyte due to the addition of liquid crystal. Besides, at-rest long-term stability shows that when liquid crystal is introduced into PVDF based polymeric gel electrolyte, DSC could retain over 92% of its initial photoelectric conversion efficiency value after 1000 h, exhibiting relatively better stability.

On the addition of conducting ceramic nanoparticles in solvent-free ionic liquid electrolyte for dye-sensitized solar cells

Titanium carbide (TiC) is an extremely hard conducting ceramic material often used as a coating for titanium alloys as well as steel and aluminum components to improve their surface properties. In this study, conducting ceramic nanoparticles (CCNPs) have been used, for the first time, in dye-sensitized solar cells (DSSCs), and the incorporation of TiC nanoparticles in a binary ionic liquid electrolyte on the cell performance has been investigated. Cell conversion efficiency with 0.6 wt% TiC reached 1.68%, which was higher than that without adding TiC (1.18%); however, cell efficiency decreased when the TiC content reached 1.0 wt%. The electrochemical impedance spectroscopy (EIS) technique was employed to analyze the interfacial resistance in DSSCs, and it was found that the resistance of the charge-transfer process at the Pt counter electrode ( R ct1) decreased when up to 1.0 wt% TiC was added. Presumably, this was due to the formation of the extended electron transfer surface (EETS) which facilitates electron transfer to the bulk electrolyte, resulting in a decrease of the dark current, whereby the open-circuit potential ( V OC) could be improved. Furthermore, a significant increase in the fill factor (FF) for all TiC additions was related to the decrease in the series resistance ( R S) of the DSSCs. However, at 1.0 wt% TiC, the largest charge-transfer resistance at the TiO 2/dye/electrolyte interface was observed and resulted from the poor penetration of the electrolyte into the porous TiO 2. The long-term stability of DSSCs with a binary ionic liquid electrolyte, which is superior to that of an organic solvent-based electrolyte, was also studied.

Binary room-temperature ionic liquids based electrolytes solidified with SiO 2 nanoparticles for dye-sensitized solar cells

In this study, binary ionic liquids (bi-IL) of imidazolium salts containing cations with different carbon side chain lengths (C = 2, 4, 6, 8) and anions such as iodide (I −), tetrafluoroborate (BF 4 −), hexafluorophosphate (PF 6 −) and trifluoromethansulfonate (SO 3CF 3 −) were used as electrolytes in dye-sensitized solar cells (DSSCs). On increasing the side chain length of imidazolinium salts, the diffusion coefficients of I 3 − and the cell conversion efficiencies decreased; however, the electron lifetimes in TiO 2 electrode increased. As for different anions, the cell which contains 1-butyl-3-methyl imidazolium trifluoromethansulfonate (BMISO 3CF 3) electrolyte has better performance than those containing BMIBF 4 and BMIPF 6. From the impedance measurement, the cell containing BMISO 3CF 3 electrolyte has a small charge transfer resistance ( R ct2 ) at the TiO 2/dye/electrolyte interface. Moreover, the characteristic frequency peak for TiO 2 in the cell based on BMISO 3CF 3 is less than that of BMIBF 4 and BMIPF 6, indicating the cell with bi-IL electrolyte based on BMISO 3CF 3 has higher electron lifetime in TiO 2 electrode. Finally, the solid-state composite was introduced to form solid-state electrolytes for highly efficient DSSCs with a conversion efficiency of 4.83% under illumination of 100 mW cm −2. The long-term stability of DSSCs with a solidified bi-IL electrolyte containing SiO 2 nanoparticles, which is superior to that of a bi-IL electrolyte alone, was also presented.

Effect of Etched Substrates in Long-Term Stability Testing of Dye-Sensitized Solar Cells

The dye-sensitized solar cells (DSSCs) examine long-term stability tests were prepared to SnO2:F (FTO) glass substrates patterned by the etching method were applied to the electrode on the device using polyethyleneglycol (PEG) electrolyte. We investigated the effect of patterned SnO2:F (FTO) glass substrates on the power conversion efficiency and long-term stability of DSSCs. The patterned devices maintained over 83% of its initial overall power conversion efficiency after 720 hours aging at room temperature, while the devices using non-patterned FTO glass substrates showed drastic decrease in performances.

Production and characterization of ITO-Pt semiconductor powder containing nanoscale noble metal particles catalytically active in dye-sensitized solar cells

Doped indium tin oxide (ITO) samples of a surface area around 60 m2/g have been synthesized. As doping component platinum and gold atoms were utilized, respectively. The powders were produced by pyrolyzing mixed metal oxide precursors in a first zone in a flame consisting of hydrogen and air, metering a noble metal compound and reducing gas into a second zone of the flame and separating off the solid obtained in a third zone. Well-defined solid phases In2Pt and In2Au in ITO were obtained, respectively. The production of a mixture with discrete SnO2 entities could be avoided. The mixed oxide powder doped with platinum can be used as a catalyst. The structure and composition of materials obtained at different levels of platinum dosing into a flame reactor has been determined. The size of the noble metal-containing entities ranged at about 3.5–5.5 nm. The catalytic properties of these oxides containing noble metal have been utilized in the fabrication of dye-sensitized solar cells (DSCs). Long term stability of DSCs containing liquid electrolytes requires a glass sealing of the two electrodes at a temperature of over 600 °C. Such high temperatures are detrimental to the catalytic activity of the conventional platinum layers in the counter electrode. Improved catalytic activity could be achieved by platinum entities bound to indium tin oxide. This catalytic material can effectively be used in the DSCs with glass sealing, the sealing temperature being over 600 °C. Spray pyrolysis in a flame reactor is highly suitable to produce noble metal-containing oxides in one single production step. Platinum-containing ITO particles from flame pyrolysis production exhibit superior catalytic activity in dye-sensitized solar cells compared to material from conventional thermal decomposition.