Tuning the HOMO energy levels of organic dyes for dye-sensitized solar cells based on Br-/Br3- electrolytes

A series of novel metal-free organic dyes TC301-TC310 with relatively high HOMO levels were synthesized and applied in dye-sensitized solar cells (DSCs) based on electrolytes that contain Br(-)/Br(3)(-) and I(-)/I(3)(-). The effects of additive Li(+) ions and the HOMO levels of the dyes have an important influence on properties of the dyes and performance of DSCs. The addition of Li(+) ions in electrolytes can broaden the absorption spectra of the dyes on TiO(2) films and shift both the LUMO levels of the dyes and the conduction band of TiO(2), thus leading to the increase of J(sc) and the decrease of V(oc). Upon using Br(-)/Br(3)(-) instead of I(-)/I(3)(-), a large increase of V(oc) is attributed to the enlarged energy difference between the redox potentials of electrolyte and the Fermi level of TiO(2), as well as the suppressed electron recombination. Incident photon to current efficiency (IPCE) action spectra, electrochemical impedance spectra, and nanosecond laser transient absorption reveal that both the electron collection yields and the dye regeneration yields (Φ(r)) depend on the potential difference (the driving forces) between the oxidized dyes and the Br(-)/Br(3)(-) redox couple. For the dyes for which the HOMO levels are more positive than the redox potential of Br(-)/Br(3)(-) sufficient driving forces lead to the longer effective electron-diffusion lengths and almost the same efficient dye regenerations, whereas for the dyes for which the HOMO levels are similar to the redox potential of Br(-)/Br(3)(-), insufficient driving forces lead to shorter effective electron-diffusion lengths and inefficient dye regenerations.     

A dye-sensitized solar cell containing an anchoring porphyrin

We have designed a self-assembly ZnP-ZnPA, based on a porphyrin ZnP bearing 1,3,5-triazine-2,4-diamine unit, and anchoring porphyrin ZnPA. The assembly with ZnP-ZnPA was immobilized on nanostructured TiO₂ electrode surfaces. The assembled structures were characterized by transmission electron microscopy. The optical, photovoltaic, electrochemical impedance spectroscopy, and incident photon-to-current conversion efficiency were measured. The results revealed that the ZnP-ZnPA device had better photovoltaic performance than ZnPA and possessed a higher shortcircuit photocurrent density (J_SC = 6.04) but a lower open-circuit photovoltage (V_OC = 0.51) than anchoring ZnPA. Moreover, our previously reported assembly (ZnP-A1) as reference, the assembly device ZnP-ZnPA had better η (2.24%) and FF (72.7%).     

Solid-state composite electrolyte LiI/3-hydroxypropionitrile/SiO2 for dye-sensitized solar cells

A new compound, LiI(3-hydroxypropionitrile)(2), is reported here. According to its single-crystal structure (C2/c), this compound has 3-D transporting paths for iodine. Further ab initio calculation shows that the activation energy for diffusion of iodine (0.73 eV) is much lower than that of lithium ion (8.39 eV) within the lattice. Such a mono-ion transport feature is favorable as solid electrolyte to replace conventional volatile organic liquid electrolytes used in dye-sensitized solar cells (DSSC). LiI and 3-hydroxypropionitrile (HPN) can form a series of solid electrolytes. The highest ambient conductivity is 1.4 x 10(-)(3) S/cm achieved for LiI(HPN)(4). However, it tends to form large crystallites and leads to poor filling and contact within porous TiO(2) electrodes in DSSC. Such a drawback can be greatly improved by introducing micrometer-sized and nanosized SiO(2) particles into the solid electrolyte. It is helpful not only in enhancing the conductivity but also in improving the interfacial contact greatly. Consequently, the light-to-electricity conversion efficiency of 5.4% of a DSSC using LiI(HPN)(4)/15 wt % nano-SiO(2) was achieved under AM 1.5 simulated solar light illumination. Due to the low cost, easy fabrication, and relatively high conversion efficiency, the DSSC based on this new solid-state composite electrolyte is promising for practical applications.     

Butyronitrile-based electrolyte for dye-sensitized solar cells

We elaborated a new electrolyte composition, based on butyronitrile solvent, that exhibits low volatility for use in dye-sensitized solar cells. The strong point of this new class of electrolyte is that it combines high efficiency and excellent stability properties, while having all the physical characteristics needed to pass the IEC 61646 stability test protocol. In this work, we also reveal a successful approach to control, in a sub-Nernstian way, the energetics of the distribution of the trap states without harming cell stability by means of incorporating NaI in the electrolyte, which shows good compatibility with butyronitrile. These excellent features, in conjunction with the recently developed thiophene-based C106 sensitizer, have enabled us to achieve a champion cell exhibiting 10.0% and even 10.2% power conversion efficiency (PCE) under 100 and 51.2 mW·cm(-2) incident solar radiation intensity, respectively. We reached >95% retention of PCE while displaying as high as 9.1% PCE after 1000 h of 100 mW·cm(-2) light-soaking exposure at 60 °C.     

Novel polysilsesquioxane-I-/I3- ionic electrolyte for dye-sensitized photoelectrochemical cells

A new sol-gel precursor, based on 1-methyl-3-[3-(trimethoxy-lambda(4)-silyl)propyl]imidazolium iodide (MTMSPI(+)I(-)), was synthesized and investigated as a potential novel quasi-solid-state ionic liquid redox electrolyte for dye-sensitized photoelectrochemical (DSPEC) cells of the Graetzel type. MTMSPI(+)I(-) was hydrolyzed with acidified water, and the reaction products of the sol-gel condensation reactions were assessed with the help of (29)Si NMR and infrared spectroscopic techniques. Results of time-dependent analyses showed the formation of a positively charged polyhedral cubelike silsesquioxane species, which still contained a small amount of silanol end groups that were removed after heating at 200 degrees C. After cooling, the material formed was a tough, yellowish, and transparent solid, consisting mainly of ladderlike polysilsesquioxane species. The specific conductivity (sigma) of the nonhydrolyzed MTMSPI(+)I(-) (no I(2)) was 0.23 mS/cm, while the activation energy (E(a)), determined from the Vogel-Tamman-Fulcher (VTF) relation, was 0.29 kJ/mol. After 56 days of aging the sigma value of the hydrolyzed MTMSPI(+)I(-) dropped to 0.11 mS/cm but the viscosity had already increased to 7500 Pa.s after 17 days, demonstrating that a quasi solid state was attained. Apparent diffusion coefficients (D(app)) of I(-) and I(3)(-) obtained from the voltammetric measurements were approximately 10(-7) cm(2)/s and decreased to approximately 10(-8) cm(2)/s after 15 days of sol aging. Time-dependent vibrational spectra, which served in assessing the hydrolysis and condensation reactions of MTMSPI(+)I(-), were measured with the help of the attenuated total reflectance (ATR) IR spectroscopic technique. The results revealed that, in the course of condensation of sols, the refractive index of the modes attributed to the polysilsesquioxane species exhibited strong dispersion, which led to a shift of the vibrational band position in the experimental ATR spectra. This effect accompanies the sol-to-gel transformations and has not yet been considered as a possible error in analysis of the ATR spectra of sols and gels. The calculation procedure for obtaining the corresponding transmission spectra is briefly outlined, and the results are applied in this work.     

Ambient temperature plastic crystal electrolyte for efficient, all-solid-state dye-sensitized solar cell

Doping the molecular plastic crystal of succinonitrile with solid N-methyl-N-butylpyrrolidinium iodide salt and iodine has produced a highly conductive solid iodide/triiodide conductor. Furthermore, it was employed for a highly efficient, all-solid-state dye-sensitized solar cell.     

High-performance quasi-solid-state dye-sensitized solar cell based on an electrospun PVdF-HFP membrane electrolyte

An electrospun membrane was prepared from a 16 wt % solution of poly(vinylidenefluoride- co-hexafluoropropylene) (PVdF-HFP) in a mixture of acetone/ N, N-dimethylacetamide (7:3 wt %) at an applied voltage of 12 kV. It was then activated by immersing it in 0.6 M 1-hexyl-2,3-dimethylimidazolium iodide, 0.1 M LiI, 0.05 M I 2, and 0.5 M 4- tert-butylpyridine in ethylene carbonate/propylene carbonate (1:1 wt %) to obtain the corresponding membrane electrolyte with an ionic conductivity of 10 (-5) S cm (-1) at 25 degrees C. On the basis of this electrospun membrane electrolyte, quasi-solid-state dye-sensitized solar cells were fabricated, which showed an open-circuit voltage ( V oc) of 0.76 V, a fill factor of 0.62, and a short-circuit current density ( J sc) of 15.57 mA cm (-2) at an incident light intensity of 100 mW cm (-2). This yields a light-to-electricity conversion efficiency of 7.3%. Moreover, this cell possessed better long-term stability than that fabricated with conventional liquid electrolyte.     

A novel composite polymer electrolyte containing room-temperature ionic liquids and heteropolyacids for dye-sensitized solar cells

A novel composite polymeric gel comprising room-temperature ionic liquids (1-butyl-3-methyl-imidazolium-hexafluorophosphate, BMImPF₆) and heteropolyacids (phosphotungstic acid, PWA) in poly(2-hydroxyethyl methacrylate) matrix was successfully prepared and employed as a quasi-solid state electrolyte in dye-sensitized solar cells (DSSCs). These composite polymer electrolytes offered specific benefits over the ionic liquids and heteropolyacids, which effectively enhanced the ionic conductivity of the composite polymer electrolyte. Unsealed devices employing the composite polymer electrolyte with the 3% content of PWA achieved the solar to electrical energy conversion efficiency of 1.68% under irradiation of 50 mW cm⁻² light intensity, increasing by a factor of more than three compared to a DSSC with the blank BMImPF₆-based polymer electrolyte without PWA. It is expected that these composite polymer electrolytes are an attractive alternative to previously reported hole transporting materials for the fabrication of the long-term stable quasi-solid state or solid state DSSCs.     

Functionalized organic dyes containing a phenanthroimidazole donor for dye-sensitized solar cell applications

Five functionalized organic dyes (H6-10) containing a phenanthroimidazole unit as an electron donor were synthesized and characterized for use in dye-sensitized solar cell (DSSC) applications. Under standard global AM 1.5 solar conditions, the DSSCs based on dye H6 displayed the best performance, with an incident photon-to-current conversion efficiency (IPCE) exceeding 70% at wavelengths of 400–530 nm, a short-circuit photocurrent density of 10.98 mA cm^?2, an open-circuit voltage of 0.68 V, a fill factor of 0.69, and an overall conversion efficiency of 5.12%. This efficiency is ～94% of that for JK2 cells (5.46%) and ～72% of that for N719 cells (7.07%) under the same conditions.     

An efficient 3C-silicon carbide/titania nanocomposite photoelectrode for dye-sensitized solar cell

Dye-sensitized solar cells (DSSCs) are fabricated using a novel 3C-SiC/TiO(2) nanocomposite as a photoelectrode to enhance the power conversion efficiency. Compared with a pristine nanocrystalline TiO(2) cell, a DSSC based on a 3C-SiC (0.04 wt%)/TiO(2) nanocomposite photoelectrode shows ~115% increase in power conversion efficiency.     

Comprehensive studies on polymer electrolyte and dye-sensitized solar cell developed using castor oil-based polyurethane

Comprehensive characterization of new polymer electrolyte system prepared using polyurethane derived from castor oil polyol was undertaken. The castor oil polyol was synthesized via transesterification and reacted with 4,4′-diphenylmethane diisocyanate to form polyurethane. Polyurethane electrolyte films were prepared by addition of sodium iodide in different weight percentage with respect to the weight of the polymer. The electrolyte films were analyzed using Fourier transform infrared spectroscopy, dynamic mechanical analysis, electrochemical impedance spectroscopy, transference number measurement, and linear sweep voltammetry. Fourier transform infrared spectroscopy results confirmed the complexation between polymer and salt. Tan delta peak observed in the tan δ–temperature curve plotted using data obtained from dynamic mechanical analysis indicated that the glass transition temperature of polyurethane decreased with the addition of sodium iodide. The highest conductivity of 4.28 × 10^?7 S cm^?1 was achieved for the film with 30 wt% of sodium iodide. The performances of dye-sensitized solar cell using the electrolyte systems were analyzed in terms of short-circuit current density, open-circuit voltage, fill factor, and energy conversion efficiency. The polymer electrolyte with 30 wt% sodium iodide showed the best performance with energy conversion efficiency of 0.80%.     

A solvent-free, SeCN-/(SeCN)3- based ionic liquid electrolyte for high-efficiency dye-sensitized nanocrystalline solar cells

A solvent-free ionic liquid electrolyte based on the SeCN-/(SeCN)3- redox couple has been employed for high-efficiency dye-sensitized nanocrystalline solar cells. For the first time an alternative redox couple has been identified to rival and even exceed the performance of the iodide/triiodide couple even at full sunlight. Unprecedented 7.5-8.3% power conversion efficiencies under AM 1.5 sunlight have been achieved for photovoltaic devices with solvent-free ionic liquid electrolytes.     

Novel photosensitizer for dye-sensitized solar cell based on ionic liquid–doped blend polymer electrolyte

The existing energy situation demands not only the huge energy in a short time but also clean energy. In this regard, an integrated photo-supercapacitor device has been fabricated in which photoelectric conversion and energy storage are achieved simultaneously. A novel carbazole-based dye is synthesized and characterized for photosensitizer. The silver-doped titanium dioxide (Ag-TiO₂) is synthesized, and it is used as photoanode material. Different concentrations of tetrabutylammonium iodide (TBAI)-doped polyvinyl alcohol–polyvinylpyrrolidone (PVA-PVP) blend polymer electrolytes are prepared, and their conductivity and dielectric properties were studied. Reduced graphene oxide (r-GO) is synthesized by a one-pot synthesis method and confirmed using Raman spectroscopy for counter electrode material in dye-sensitized solar cell (DSSC) and supercapacitor electrodes. The DSSC having 4% Ag-TiO₂–based photoanode showed the highest efficiency of 1.06% (among r-GO counter electrodes) and 2.37% (among platinum counter electrodes). The supercapacitor before integration and after integration exhibits specific capacitance of 1.72 Fg⁻¹ and 1.327 Fg⁻¹, respectively.

Graphical Abstract

     

一种不含胶凝剂的凝胶电解质在准固态染料敏化太阳能电池中的应用

报道了一种不含胶凝剂的凝胶电解质的制备及在准固态染料敏化太阳能电池中的应用.这种新型凝胶电解质仅含有机溶剂和碘盐,即3-甲氧基丙腈、苯胺、三碘化铝和碘.上述混合物通过路易斯酸性三碘化铝离子导体和路易斯碱性苯胺有机溶剂间的路易斯酸-碱相互作用形成凝胶,无需额外添加传统凝胶电解质的关键组分—胶凝剂.形成的三碘化铝-苯胺复合物在凝胶电解质中能同时发挥离子导体和胶凝剂的作用.红外光谱图中苯胺的氨基和苯环特征峰的变化证实了三碘化铝-苯胺复合物的形成.含这种新型凝胶电解质的准固态染料敏化太阳能电池光电性能和稳定性与含三碘化铝-3-甲氧基丙腈液体电解质的染料敏化太阳能电池相比有很大提高.     

Gelation of a liquid electrolyte with aniline for use in a quasi-solid-state dye-sensitized solar cell

A new kind of gel electrolyte containing only organic solvents and an iodide salt-namely 3-methoxypropionitrile(MPN),aniline and AlI 3 -has been prepared.Gel formation results from the Lewis acid-base interaction between the Lewis acid ionic conductor AlI 3 and the Lewis base organic solvent aniline and no additional gelling agent is required.The AlI 3-aniline complex acts both as an ionic conductor and as a gelling agent.The differences between the peaks characteristic of the-NH 2 group and aromatic ring in the FTIR spectra of free aniline and the AlI 3-aniline hybrid confirm the formation of the AlI 3-aniline complex.The photovoltaic performance and long-term stability of dye-sensitized solar cells can be greatly enhanced by the addition of aniline to the AlI 3-MPN liquid electrolyte.     

Efficient non-corrosive electron-transfer mediator mixtures for dye-sensitized solar cells

The electrochemical and photoelectrochemical study of noncorrosive electron-transfer mediator mixtures for DSC is reported. These mixtures, characterized by the presence of kinetically fast organic or metal-organic redox couples in conjunction with a Co(II)/(III) relay, exhibited maximum photon-to-current conversion efficiencies (IPCE %) exceeding 80% when employed in the presence of a suitably designed MLCT sensitizer, rivaling with the performances of the classical I-/I3- electrolyte.     

Efficient iodine-free dye-sensitized solar cells employing truxene-based organic dyes

Two new truxene-based organic sensitizers (M15 and M16) featuring high extinction coefficients were synthesized for dye-sensitized solar cells employing cobalt electrolyte. The M16-sensitized device displays a 7.6% efficiency at an irradiation of AM1.5 full sunlight.     

Quasi-solid-state dye-sensitized solar cell based on a polymer gel electrolyte with in situ synthesized ionic conductors

A polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors was prepared for fabricating a quasi-solid-state dye-sensitized solar cell (QS-DSSC). The in situ synthesized Acac-Py-I₂ ionic conductors show weaker influence on the liquid electrolyte absorbency of the polymer gel electrolyte than that of Acac-Py-I₂ ionic conductors dissolved in liquid electrolyte. Owing to the higher liquid electrolyte absorbency, the polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors shows higher ionic conductivity than that of polymer gel electrolyte with Acac-Py-I₂ ionic conductors absorbed from liquid electrolyte. QS-DSSC containing the polymer gel electrolyte with in situ synthesized Acac-Py-I₂ ionic conductors shows 3.815% energy conversion efficiency, which is 21.6% higher than that of QS-DSSC containing polymer gel electrolyte with Acac-Py-I₂ ionic conductors absorbed from liquid electrolyte.     

A promising heat-induced supramolecular metallogel electrolyte for quasi-solid-state dye-sensitized solar cells

Journal of Solid State Electrochemistry - A series of Fe(III)-based coordination-driven metallogel (MOG) electrolytes are obtained by absorbing liquid electrolytes with MOGs and applied to...     

Stable mesoscopic dye-sensitized solar cells based on tetracyanoborate ionic liquid electrolyte

A stable dye-sensitized solar cell has been obtained based on a new binary ionic liquid electrolyte system containing 1-propyl-3-methylimidazolium iodide and 1-ethyl-3-methylimidazolium tetracyanoborate.