Stability Of Dye-sensitized Solar Cells Research Articles

Insight into D-A-π-A Structured Sensitizers: A Promising Route to Highly Efficient and Stable Dye-Sensitized Solar Cells.

The dye-sensitized solar cell (DSSC) is one of the most promising photovoltaic technologies with potential of low cost, light weight, and good flexibility. The practical application of DSSCs requires further improvement in power conversion efficiency and long-term stability. Recently, significant progress has been witnessed in DSSC research owing to the novel concept of the D-A-π-A motif for the molecular engineering of organic photosensitizers. New organic and porphyrin dyes based on the D-A-π-A motif can not only enhance photovoltaic performance, but also improve durability in DSSC applications. This Spotlight on Applications highlights recent advances in the D-A-π-A-based photosensitizers, specifically focusing on the mechanism of efficiency and stability enhancements. Also, we find insight into the additional acceptor as well as the trade-off of long wavelength response. The basic principles are involved in molecular engineering of efficient D-A-π-A sensitizers, providing a clear road map showing how to modulate the energy bands, rationally extending the response wavelength, and optimizing photovoltaic efficiency step by step.

Thermal stability and electrical studies on hybrid and composite sol–gel quasi-solid-state electrolytes for dye-sensitized solar cells

Nanocomposite organic/inorganic materials made through sol–gel method can be applied as quasi-solid-state electrolytes aiming to overcome the common issues of evaporation, leaking and stability in dye-sensitized solar cells. Two different kinds of quasi-solid-state electrolytes, depending on the different interactions between silica as inorganic phase and organic substances such as polyethylene/or polypropylene oxide derivatives, are prepared by the sol–gel technique in room temperature. Release dynamics of volatile components from two types of quasi-solid-state electrolytes are studied by thermogravimetry (TG) in order to predict the stability or changes in composites during their application in dye-sensitized solar cells. Two online coupled evolved gas analytical tools (TG-EGA-FTIR and TG/DTA-EGA-MS) are applied to test the gel electrolytes for accelerated thermal vaporization, degradation and decomposition processes as a function of temperature during dynamic heating in air. Stable solar cells based on the different quasi-solid-state electrolytes are constructed and characterized with current density curves exhibiting overall efficiencies varying from 2.9 to 4.2 % for thin TiO2 films sensitized with standard commercial dye.

Enhanced dye stability in dye-sensitized solar cells using 1D-structured titanate

Hydrogen titanate nanowires were synthesized for exploiting their high injection efficiency in dye-sensitized solar cells and the degradation of a dye in the presence of the nanowires under UV irradiation was evaluated. The band-gap energy of the hydrogen titanate nanowires was 3.9eV, which was much higher than that of commercial P25 TiO2 nanoparticles. Dye degradation of 40% was achieved with the nanowires, whereas P25 nanoparticles induced 70% degradation of the dye under UV irradiation. Thus, hydrogen titanate nanowires may prospectively be used as a photoanode material in dye-sensitized solar cells to minimize dye and electrolyte degradation by photocatalytic oxidation.

Krokot Extract (Portulaca Oleracea. L) as Natural Light-harvesting pigments for Dye-Sensitized Solar Cells (DSSCs) : Influence of Dye Acidity

Dye-sensitized solar cells (DSSCs) was fabricated using natural dyes extracted from krokot (Portulaca Oleracea. L). The effect of dye acidity was investigated on natural pH extract, 5.00, 4.00 and 3.00 of pH. The efficiency and stability DSSCs as a function of the dye acidity was studied. The result of the UV-Vis shows that the absorption of wave-length from dye extract of krokot is located in the visible region with the absorbance peak in 410.5 nm and 664.5 nm which are the peak of chlorophyll. The efficiency of extract krokot dye sensitized solar cells was decreasing 6.88 x 10<sup>-3</sup> % to 0.42 x 10<sup>-3</sup> % when pH of the dye was adjusted from 6.27 to 3.00. DSSCs stability was also decreased look for efficiency loss from 5.27% to 97.49% in the same conditions.

Highly catalytic nickel sulfide counter electrode for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) have been the epicenter of attention for past few decades as a potentially cost-effective substitute for silicon-based solar cells. In DSSCs, the counter electrode (CE) plays a pivotal role in amassing electrons from the external circuit and catalyzing the I3− reduction in the electrolyte. In this paper, the development of nickel sulfide (NiS) CEs for DSSCs are studied, emphasizing significant crescendos that assure economical, competent, and stable DSSC systems. Specially, we pinpoint on the design of highly efficient NiS CE, including design ideas, fabrication approaches and characterization techniques that serve as practical replacements to conventional noble metal Pt electrodes. DSSC fabricated with the NiS CE achieved a power conversion efficiency of 5.69% under 1 sunlight illumination (100 mW cm−2, AM 1.5 G).

Synthesis and Photovoltaic properties of branched chain polymeric metal complexes containing Phenothiazine and Thiophene derivative for dye-sensitized solar cells

Three donor-π-acceptor (D-π-A) dyes (P1–P3) of polymeric metal complexes were synthesized for application in dye-sensitized solar cells (DSSCs). These D-π-A sensitizers use Phenothiazine appended with octyl as donor (D), C=C bond as π-bridge(π), and thiophene-phenanthroline metal complexes as acceptor (A) that can be anchored to the TiO2 surface. They have been characterized and studied by FT-IR, GPC, Elemental analysis, TGA, UV-vis absorption spectroscopy, photoluminescence spectroscopy and cyclic voltammetry. When applied in the DSSCs, the sensitizer P1 exhibits the best energy conversion efficiency of 1.57% (Jsc = 4.12 mA/cm2, Voc = 0.62 V, FF = 61.7%) under simulate AM 1.5G solar irradiation. The TGA data show that these new dyes own good thermal stability. These results will facilitate the understanding of the crucial importance of molecular engineering and pave a new path to design novel conjugated organic polymer dye for highly efficient and stable DSSCs. Three D-π-A sensitizers that use Phenothiazine appended with octyl as donor, C=C bond as π-bridge, and thiophene-phenanthroline metal complex as acceptor were synthesized. When applied in a dye sensitized solar cell, the sensitizer P1 exhibits the best energy conversion efficiency of 1.57% under simulated AM 1.5G solar irradiation.

A New Method for Preparation of TiO2 Nanowire Array-Based Photoanodes for Stable Dye-Sensitized Solar Cells

A New Method for Preparation of TiO2 Nanowire Array-Based Photoanodes for Stable Dye-Sensitized Solar Cells

The Effect of Electrolyte Purification on the Performance and Long-Term Stability of Dye-Sensitized Solar Cells

In this study the effect of the purification of electrolyte material on the performance and long-term stability of dye-sensitized solar cells is investigated. The combined effect of purifying all the electrolyte materials has been examined, as has the effect of purifying each compound to identify those compounds worth purifying and to eliminate unnecessary production steps on an industrial scale. Statistical methods were employed to draw statistically significant conclusions from the experimental results. No effect on the initial cell performance is found in this study. The purity of the electrolyte solvent (here methoxypropionitrile) is shown to have a remarkable effect on the cell lifetime: it could even double when the cell is properly purified. It is shown that exposing the cell to even relatively small amounts of UV light resulted in cell degradation through electrolyte bleaching during a 1000 hour aging test. Here the impurities in the electrolyte solvent lead to an almost doubled rate of electrolyte bleaching under UV light.

Enhancement of the outdoor stability of dye-sensitized solar cells by a spectrum conversion layer with 1,8-naphthalimide derivatives

DSSC using 1,8-naphthalimide derivatives maintained 18% higher relative photo-conversion efficiency after 48 days outdoor condition than DSSC using commercial UV cut-off filter.

Thiazolo[5,4-d]thiazole-based organic sensitizers with strong visible light absorption for transparent, efficient and stable dye-sensitized solar cells

Five thiazolothiazole-based dyes, bearing electronrich ProDOT groups, were used as sensitizers in thin-layer DSSCs (active area: 0.25–3.6 cm2; TiO2 thickness: 3.0–6.5 μm), giving efficiencies up to 7.71% coupled with excellent stability over 1000 h.

Direct light-induced polymerization of cobalt-based redox shuttles: an ultrafast way towards stable dye-sensitized solar cells.

The photopolymerization of Co(II)/Co(III) complexes for dye-sensitized solar cells (DSSCs) by means of a fast, inexpensive, in situ and inhibition-free process has been examined. We have succeeded in fabricating high-performance DSSCs able to retain a light-to-electricity power conversion efficiency exceeding 6.5% (8.5% at low intensity) after 1800 h of mixed (light on/off, temperature high/low) accelerated aging tests, thus revealing a possible way for the stabilization of these record-holding redox pairs.

Dipicolinic acid: a strong anchoring group with tunable redox and spectral behavior for stable dye-sensitized solar cells.

Dipicolinic acid was investigated as a new anchoring group for DSSCs. A pilot dye (PD2) bearing this new anchoring group was found to adsorb significantly stronger to TiO2 than its cyanoacrylic acid analogue. The electrolyte composition was found to have a strong effect on the photoelectrochemical properties of the adsorbed dye in the device, allowing the dye LUMO energy to be tuned by 0.5 eV. Using a pyridine-free electrolyte, panchromatic absorption of the dye on TiO2 extending to 900 nm has been achieved. Solar cells using PD2 and a Co(bpy)3 based electrolyte showed unique stability under simulated sunlight and elevated temperatures.

A Review on Current Status of Stability and Knowledge on Liquid Electrolyte-Based Dye-Sensitized Solar Cells

The purpose of this review is to gather the current background in materials development and provide the reader with an accurate image of today’s knowledge regarding the stability of dye-sensitized solar cells. This contribution highlights the literature from the 1970s to the present day on nanostructured TiO2, dye, Pt counter electrode, and liquid electrolyte for which this review is focused on.

Functional titanium oxide nano-particles as electron lifetime, electrical conductance enhancer, and long-term performance booster in quasi-solid-state electrolyte for dye-sensitized solar cells

This research investigates the design of a quasi-solid-state electrolyte for improving the photovoltaic efficiency and long-term performance stability of dye-sensitized solar cells (DSSCs). In this study, agarose gel and titanium oxide (TiO2) nano-particles are incorporated into an iodine/iodide electrolyte solution in a 1-methyl-2-pyrrolidinone (NMP)/3-methoxypropionitrile (MPN) solvent mixture to fabricate quasi-solid-state electrolytes for 2.0-cm2 DSSCs. The electrolyte also contains an ionic liquid, 1-methyl-3-propylimidazolium iodide, and a co-additive, 1-methylbenzimidazole. The negatively charged TiO2 nano-particles exhibit an anatase crystal structure. Without agarose and TiO2, the control cell's photovoltaic efficiency drops by more than 50% over 2400 h of aging due to a significant decrease in the short-circuit current. Incorporating 1% agarose into the electrolyte not only enhances the retention of the solvent but also maintains the short-circuit current. Furthermore, adding 0.5% TiO2 to 1% agarose electrolyte provides sufficient ion and electron transfer routes and improves the fill factor of the corresponding DSSC. The photoconversion efficiency of the agarose/TiO2-containing DSSC monotonically increases from an initial value of 5.08% to 6.48% within 2400 h. The improved cell efficiency is correlated to the longer electron lifetime in the DSSC, higher ion diffusivity, and the smaller electrical resistance of the electrolyte.

Highly stable dye-sensitized solar cells with quasi-solid-state electrolyte based on Flemion

A polymer gel electrolyte containing Flemion® (a perfluorocarboxylated polymer) as polymer matrix, lithium iodide, iodine, 1,2 dimethyl-3-propylimidazolium iodide (DMPII) and 4-tert-butylpyridine (TBP) was developed for quasi-solid-state dye-sensitized solar cells (DSSCs). The Flemion-based electrolyte was gelled by heating the Flemion solution to evaporate the ethanol solvent. Scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy suggested three regions in the Flemion-based gel electrolyte: the fluorocarbon polymer frame, the ion cluster, and their interface. The open-circuit voltage, the short-circuit current density, and the fill factor were markedly enhanced by adding TBP and DMPII, respectively, to the Flemion-based gel electrolyte. When irradiated with light at 100mWcm−2, the DSSC containing the Flemion-based gel electrolyte with 0.6M DMPII and 0.5M TBP exhibited an energy conversion efficiency (η) of 4.1%, while η of the acetonitrile-based DSSC was 5.1%. According to electrochemical impedance spectra, gelation greatly increased the charge transfer resistance at the TiO2/electrolyte interface in DSSCs containing the Flemion-based electrolyte without DMPII. However, this effect was negated by adding 0.6M DMPII to the electrolyte. The η of Flemion-gel-based DSSCs stored for up to 4392h decreased by less than 10%. In contrast, the η of Flemion-liquid-based and acetonitrile-based DSSCs decreased by 95% during 480h storage, and by 93% during 115h storage, respectively. This result demonstrates that Flemion-based gel electrolytes solve the leakage problem that degrades the performance of DSSCs.

Stability of ruthenium/organic dye co-sensitized solar cells: a joint experimental and computational investigation

We carried out a joint experimental and theoretical study of the stability of dye-sensitized solar cells using a mixture of black dye (N749) and a Y1 organic co-adsorbent. The aim of this work was to investigate the stability of these highly efficient sensitizers. The co-sensitized device showed remarkable stability under the conditions investigated (1100 h of about 1 Sun light soaking at 55 °C). The partial desorption of the organic co-adsorbent was identified as a possible cause of the slight reduction in the photocurrent value. Theoretical investigations on the dye-sensitized semiconductor surface using DFT methods showed a considerably lower adsorption energy for Y1 compared with N749, in particular upon oxidation, possibly leading to desorption of the dye under working conditions. The devices using only the Y1 organic dye consistently showed a considerably lower stability.

Multifunctional Luminescent Down‐Shifting Fluoropolymer Coatings: A Straightforward Strategy to Improve the UV‐Light Harvesting Ability and Long‐Term Outdoor Stability of Organic Dye‐Sensitized Solar Cells

A new multifunctional coating for photovoltaic cells incorporating light‐management, UV‐protection, and easy‐cleaning capabilities is presented. Such coating consists of a new photocurable fluorinated polymer embedding a luminescent europium complex that acts as luminescent down‐shifting (LDS) material converting UV photons into visible light. The combination of this system with ruthenium‐free organic dye‐sensitized solar cells (DSSCs) gives a 70% relative increase in power conversion efficiency as compared with control uncoated devices, which is the highest efficiency enhancement reported to date on organic DSSC systems by means of a polymeric LDS layer. Long‐term (>2000 h) weathering tests in real outdoor conditions reveal the excellent stabilizing effect of the new coating on DSSC devices, which fully preserve their initial performance. This excellent outdoor stability is attributed to the combined action of the luminescent material that acts as UV‐screen and the highly photostable, hydrophobic fluoropolymeric carrier that further prevents photochemical and physical degradation of the solar cell components. The straightforward approach presented to simultaneously improve performance and outdoor stability of DSSC devices may be readily extended to a large variety of sensitizer/luminophore combinations, thus enabling the fabrication of highly efficient and extremely stable DSSCs in an easy and versatile fashion.

New insights in long-term photovoltaic performance characterization of cellulose-based gel electrolytes for stable dye-sensitized solar cells

The gelation of ionic liquid-based solutions with inorganic or organic fillers is one of the strategies commonly adopted in the Dye-Sensitized Solar Cells (DSSCs) field for preparing quasi-solid electrolytes characterized by good photovoltaic performance and long-term stability. In the present paper, the application of a gel electrolyte based on unmodified microcrystalline cellulose and ionic liquids in a DSSC is reported. The gel electrolyte has been characterized evaluating its conductive, thermogravimetric, viscous and crystalline properties, while the photoelectrochemical behavior of the quasi-solid DSSCs has been investigated measuring current-voltage, Electrochemical Impedance Spectroscopy and Linear Sweep Voltammetry curves. The photovoltaic performance of cellulose gel-based DSSCs has been optimized by monitoring some key parameters, such as ionic liquid volume ratios and cellulose content. A maximum photoconversion efficiency of 3.33% has been obtained with the total absence of organic solvents, and a good stability has been demonstrated during more than 8 hours of exposition (replicated over months) to simulated solar light. Moreover, a peculiar and reversible trend in the short-circuit current density and in the overall efficiency of the cell has been observed during prolonged photovoltaic measurements. The present findings suggest the necessity to adopt a new protocol for the measurement of the photovoltaic parameters of quasi-solid DSSCs.

Printable ternary component polymer-gel electrolytes for long-term stable dye-sensitized solar cells

ABSTRACT Printable ternary component polymer-gel electrolytes (TCPGEs) including low-volatile liquid solvent, polymer additive, and nano-fillers were prepared for a facile manufacturing of long-term stable dye-sensitized solar cells (DSSCs). The viscosity range of the TCPGEs was tuned to a similar viscosity range of a commercial paste for screen printing by adding poly(ethylene oxide) (PEO, M w =300,000 g mol −1 ) and TiO 2 nanoparticles ( d =∼20 nm). The addition of PEO increased the V OC while the nano-filler facilitated the redox ion transport. Meanwhile, the introduction of nano-fillers significantly reduced the optimum I 2 concentration compared to those of liquid and polymer-gel electrolytes, which is also beneficial for the low light absorption as well as the high durability of a module with metal grids. The DSSC employing the TCPGE of the optimal composition, exhibited the maximum energy conversion efficiency of 9.2% at one sun illumination. In addition, the use of the TCPGEs promised excellent durability under a light-soaking at 60 °C for 300 hrs, which is better than that of the cell employing liquid electrolyte.

Inside Cover: Coupled Near- and Far-Field Scattering in Silver Nanoparticles for High-Efficiency, Stable, and Thin Plasmonic Dye-Sensitized Solar Cells (ChemSusChem 9/2014)

Inside Cover: Coupled Near- and Far-Field Scattering in Silver Nanoparticles for High-Efficiency, Stable, and Thin Plasmonic Dye-Sensitized Solar Cells (ChemSusChem 9/2014)