Mesoporous Carbon Counter Electrode Research Articles

Designing highly effective mesoporous Carbon-based counter electrodes for liquid Electrolyte-based and Quasi-solid Dye-sensitized solar cells

In this study, nitrogen-doped mesoporous carbon (NMC) and boron-doped mesoporous carbon (BMC) are synthesized and used as Pt-free counter electrode (CE) materials for dye-sensitized solar cells (DSCs). The optimized NMC and BMC CEs exhibit significantly higher catalytic activities than the pristine mesoporous carbon (MC). The I-/I3- in acetonitrile liquid electrolyte-based DSCs have power conversion efficiencies (PCE) of 7.20% with the NMC CE and 7.15% with the BMC CE, which are significantly higher than that obtained using the MC CE (5.88%). This is attributed to the improved effective catalytic active sites and the enhanced electrical conductivities of the NMC and BMC CEs. When Pt with trace amounts (0.1 wt%) is loaded on NMC, the liquid DSCs using Pt/NMC composite CEs yield PCE values of 8.31% and 9.92%, respectively, under 1.0 Sun and 0.1 Sun illumination. The Pt/NMC CE is further employed in quasi-solid DSCs, which also give a high PCE of 8.15% under 1.0 Sun illumination. A flexible Pt/NMC CE is also prepared on indium tin oxide-polyethylene naphthalate (ITO-PEN) substrate, and the generated liquid DSCs show a PCE of 6.92%. This work provides a feasible path to enhance the catalytic activity of the MC CE in DSCs.

An integrated approach to construct tantalum derivatives for electrocatalysis beyond the triiodide reduction reaction

The counter electrode (CE) is an essential component in dye-sensitized solar cells (DSSCs) to transfer electrons and catalyze triiodide reduction. In this research, efficient and cost-effective tantalum derivatives (oxide, nitride, carbide, oxynitride, and corresponding hybrids) are synthesized and utilized as CEs in DSSCs toward the triiodide reduction. The DSSC with mixed-anionic TaON CE achieves a cell efficiency of 5.46%, surpassing that with pristine TaOx CE (5.20%) before nitriding treatment. Benefiting from the synergistic interaction between mesoporous carbon (MC) and TaC0.95, TaC0.95/MC hybrid CE-based DSSC possess superior cell efficiency of 7.23%, higher than that of respective TaC (6.24%) and MC (6.52%), especially standard Pt (6.34%). Furthermore, TaON and TaC0.95/MC CEs exhibit durably great catalytic activity for I3- reduction. This work raises an effective and generally accepted approach to construct transition metal derivatives, which could utilize as low-priced Pt-free electrocatalysts for new energy devices.

Extending lead-free hybrid photovoltaic materials to new structures: thiazolium, aminothiazolium and imidazolium iodobismuthates.

We report on the synthesis, crystal structures, optoelectronic properties and solar cell device studies of three novel organic-inorganic iodobismuthates - [C3H4NS]3[Bi2I9] ([TH]3[Bi2I9]), [C3H4N2]3[Bi2I9] ([IM]3[Bi2I9]) and [C3H5N2S][BiI4] ([AT][BiI4]) as lead-free light harvesters. [TH]3[Bi2I9] and [IM]3[Bi2I9] show zero-dimensional structures, whereas a one-dimensional edge-sharing chain structure of BiI6-octahedra was observed in [AT][BiI4], with interchain short II contacts also giving rise to the possibility of three-dimensional charge transport ability. Accordingly, greater energy dispersion in the band structure of [AT][BiI4] can be observed, and less contribution from the organic moities at the conduction band minimum in [AT][BiI4] than [TH]3[Bi2I9] have been confirmed by density functional theory calculations. Moreover, bandgap values are redshifted from 2.08 eV for [TH]3[Bi2I9] and 2.00 eV for [IM]3[Bi2I9] to 1.78 eV for [AT][BiI4], determined by UV-Vis reflectance spectroscopy. Power conversion efficiency of 0.47% has been achieved by using ([AT][BiI4]) as the light absorber in a hole-conductor-free, fully printable solar cell, with relatively good reproducibility. We also note the observation of a capacitance effect for the first time in a photovoltaic device with bismuth-based solar absorber, which may be related to the mesoporous carbon counter-electrode.

Alloying Strategy in Cu-In-Ga-Se Quantum Dots for High Efficiency Quantum Dot Sensitized Solar Cells.

I-III-VI2 group "green" quantum dots (QDs) are attracting increasing attention in photoelectronic conversion applications. Herein, on the basis of the "simultaneous nucleation and growth" approach, Cu-In-Ga-Se (CIGSe) QDs with light harvesting range of about 1000 nm were synthesized and used as sensitizer to construct quantum dot sensitized solar cells (QDSCs). Inductively coupled plasma atomic emission spectrometry (ICP-AES), wild-angle X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses demonstrate that the Ga element was alloyed in the Cu-In-Se (CISe) host. Ultraviolet photoelectron spectroscopy (UPS) and femtosecond (fs) resolution transient absorption (TA) measurement results indicate that the alloying strategy could optimize the electronic structure in the obtained CIGSe QD material, thus matching well with TiO2 substrate and favoring the photogenerated electron extraction. Open circuit voltage decay (OCVD) and impedance spectroscopy (IS) tests indicate that the intrinsic recombination in CIGSe QDSCs was well suppressed relative to that in CISe QDSCs. As a result, CIGSe based QDSCs with use of titanium mesh supported mesoporous carbon counter electrode exhibited a champion efficiency of 11.49% (Jsc = 25.01 mA/cm2, Voc = 0.740 V, FF = 0.621) under the irradiation of full one sun in comparison with 9.46% for CISe QDSCs.

Mesoporous carbon counter electrode materials for dye-sensitized solar cells: The effect of structural mesopore ordering

Abstract Highly ordered, ordered and disordered mesoporous carbons were prepared by an organic–organic self-assembly method with different molar ratios of formaldehyde to resorcinol (F/R) under the catalysis of citric acid. The mesoporous carbon synthesized with the F/R ratio of 2 possesses highly ordered pore system and large surface area, while the ones with the F/R ratio of 1 and 3 have an ordered and a disordered wormhole-like mesostructure, respectively. These three kinds of mesoporous carbons were utilized as counter electrode (CE) materials for dye-sensitized solar cells (DSSCs) and the effect of structural mesopore ordering on the photovoltaic performance was investigated. The cell assembled with highly ordered mesoporous carbon CE showed an excellent energy conversion efficiency of 6.06%, which is comparable to the one with Pt CE (6.29%), whereas ordered mesoporous carbon and disordered mesoporous carbon CEs based cells exhibited relatively poor photovoltaic performance at the same testing conditions. The enhanced catalytic capability of highly ordered mesoporous carbon CE is intrinsically attributed to the straight channels of long-range highly ordered 2-D hexagonal mesopores, which accelerates the diffusion of redox species and facilitates the charge-transfer process. The synthesized highly ordered mesoporous carbon with outstanding catalytic activity could be an alternative to replace Pt for high-efficiency DSSC CE.

In-situ formation of dispersed ZnO nanoparticles in mesoporous carbon counter electrode for efficient dye-sensitized solar cells

The high electronic-mobility ZnO was developed as binder with a mesoporous carbon (MC) as catalytic material to fabricate a novel ZnO–MC counter electrode through in-situ formation technique. The homogeneous MC blended paste containing the ZnO sol was first coated on the conductive substrate, and then annealed in ambient atmosphere to obtain the ZnO–MC electrode. The annealing temperature is a key factor to obtain the high-performance ZnO–MC electrode. When annealed at 300°C, the in-situ formed and dispersed ZnO nanoparticles are functioned as bridges to bind the MC particles and to strengthen the adhesion of the carbon film to the substrate, providing enough conductive paths for the transportation of the electrons to participate timely in the reduction of tri-iodide (I3−), and further improving the electrochemical performances of the electrode. As a result, the efficiency of the ZnO–MC electrode for use in dye-sensitized solar cells (DSCs) enhances from 2.5% to 6.37% compared with the binder-free MC electrode. Importantly, the ZnO–MC electrode exhibits higher catalytic activity for the I3− reduction than the MC electrode using carboxymethyl cellulose (CMC) as binder, leading to an increase of 14.2% in the efficiency of the cell, which is mainly from the high electronic-mobility of the ZnO. Furthermore, the efficiency of the low cost ZnO–MC based DSCs reaches 90.4% of that of the Pt based ones. Noted that compared with the Pt electrode, the ZnO–MC electrode is beneficial to obtain a device with higher open-circuit voltage.

Direct tri-constituent co-assembly of highly ordered mesoporous carbon counter electrode for dye-sensitized solar cells

Controlling over ordered porosity by self-assembly is challenging in the area of materials science. Materials with highly ordered aperture are favorable candidates in catalysis and energy conversion device. Here we describe a facile process to synthesize highly ordered mesoporous carbon (OMC) by direct tri-constituent co-assembly method, which uses resols as the carbon precursor, tri-block copolymer F127 as the soft template and tetraethoxysilane (TEOS) as the inorganic precursor. The obtained products are characterized by small-angle X-ray diffraction (SAXD), Brunauer-Emmett-Teller (BET) nitrogen sorption-desorption measurement and transmission electron microscope (TEM). The results indicate that the OMC possesses high surface areas of 1209 m(2) g(-1), homogeneous pore size of 4.6 nm and a large pore volume of 1.65 cm(3) g(-1). The advantages of high electrochemical active surface area and favorable accessible porosity of OMC benefit the catalysis of I(3)(-) to I(-). As a result, the OMC counter electrode displays a remarkable property when it was applied in dye-sensitized solar cells (DSSCs). For comparison, carbon black (CB) counter electrode and Pt counter electrode have also been prepared. When these different counter electrodes were applied for dye-sensitized solar cells (DSSCs), the power-conversion efficiency (η) of the DSSCs with CB counter electrode are measured to be 5.10%, whereas the corresponding values is 6.39% for the DSSC with OMC counter electrode, which is comparable to 6.84% of the cell with Pt counter electrode under the same experimental conditions.

Incorporating conductor paste in a low-temperature fabrication process for large mesoporous carbon counter electrode in dye-sensitized solar cells

A novel silver conductor paste modified mesoporous carbon (SCP-MC) counter electrode has been fabricated at low temperature using a large pore MC as catalytic material and the SCP as binder. The efficiency of dye-sensitized solar cells (DSCs) employing the SCP-MC counter electrode reaches the maximum of 5.93% when the SCP content is 6wt.%, which is 15.4% higher than that of DSCs with a pure MC counter electrode. The improved efficiency mainly results from the enhancement in the fill factor and the short-circuit photocurrent density. Electrochemical impedance spectroscopy (EIS) reveals evident decreases in charge transfer resistance, ohmic serial resistance and Nernst diffusion impedance of the SCP-MC electrode with the SCP content increasing. The contacts among the MC particles and between the catalytic film and the substrate are improved by introducing the SCP, which play a key role in reducing the impedance parameters of the SCP-MC electrode and further improving the photovoltaic parameters of the cells. Especially, the DSCs with the optimum SCP-MC electrode have comparable efficiency to the DSCs with Pt electrode under the same conditions. The high performance of the SCP-MC electrode can be attributed to the favorable characteristics of the MC, such as large sized mesopores, high surface area and low crystallinity as well as the high quality catalytic film caused by adding the SCP.

Optimization of Dye-sensitized Solar Cells Consisting of Low-temperature Fabricated Mesoporous Carbon Counter Electrode

Carbon counter electrode was fabricated using high surface area mesoporous carbon (MC) as catalytic ma- terial at low temperature. The integral structure and the photovoltaic performances of dye-sensitized solar cells (DSC) consisting of the obtained carbon counter electrode were emphatically optimized. The results show that both contact interface among MC particles and that between carbon catalytic film and substrate are improved by adding Triton X100 into MC slurry, leading to an increase of 7.1% in the efficiency of DSC. With the increasing thickness of TiO2 film, the efficiency of DSC sharply increases at first and tends to stabilization later on. The change in the efficiency is the result of competition between the adsorption amount of dye and the transmission path of electron in the TiO2 film. The resistance of electrolyte is reduced by mixing tributyl phosphate into electrolyte, resulting in an increase of 23.1% in the efficiency of DSC. The optimum efficiency of DSC employing carbon counter electrode reaches 4.82%.

Preparation and Property of Hierarchical Porous Carbon Counter Electrode for Dye-sensitized Solar Cells

Hierarchical porous carbon(HPC) was prepared by the combination of self-assembly and post activation.The analysis of N2 adsorption isotherm for carbon samples indicated that large quantities of micropores were gener-ated within the mesopore wall of mesoporous carbon.HPC electrode exhibited high electrocatalytic activity for I3-reduction due to its high surface area and unique hierarchical porous structure.Electrochemical impedance spec-troscopy measurement indicated that the charge-transfer resistance of HPC electrode was 0.3 ?.cm2.The short-circuit current density,the open-circuit voltage and the fill factor of dye-sensitized solar cell with HPC counter electrode were 0.624 V,15.44 mA/cm2 and 0.67,respectively.The overall conversion efficiency of the dye-sensitized solar cell with HPC counter electrode is 6.48%,which is 11.5% higher than that of the cell with mesoporous carbon counter electrode.

Solar Energy Conversion by Dye-Sensitized Photovoltaic Cells Using High Surface Area Mesoporous Carbon Counter Electrode

Development of new counter electrode materials is vital for commercialization of efficient dye-sensitized solar cells (DSCs) process. Research on DSCs has been focused mainly on using platinum as counter electrode, which makes them expensive. In this paper, we report DSCs fabricated with high surface area mesoporous carbon thin film with uniform spherical particles as counter electrode. An overall light-to-electricity efficiency as high as 7.6% has been achieved under illumination of air mass (AM) 1.5 sunlight (100 mW/cm2). In comparison with activated carbon, high surface area mesoporous carbon shows superior performance. Our results show that mesoporous carbon with high specific surface area and uniform pore size distribution proved to be better efficient electrode material for DSCs.

Micro–meso hierarchical porous carbon as low-cost counter electrode for dye-sensitized solar cells

A micro–meso hierarchical porous carbon with low crystallinity was prepared by a combination of self-assembly and post activation and explored as a counter electrode in dye-sensitized solar cells. Pore structure analysis showed that the pristine mesopores were basically preserved during activation and the micropores were mainly generated within the mesopore wall. Due to its low crystallinity and unique pore-structure including both mesopores and micropores, hierarchical porous carbon exhibited a relatively higher electrocatalytic activity for triiodide reduction, as compared with the pristine mesoporous carbon electrode. This enhanced electrocatalytic activity is beneficial for improving the photovoltaic performance of dye-sensitized solar cells. Under irradiation of 100 mW cm −2, the dye-sensitized solar cell with hierarchical porous carbon counter electrode showed an overall conversion efficiency of 6.48%, which was 11.5% higher than that of the cell with pristine mesoporous carbon counter electrode.

Low temperature fabrication of flexible carbon counter electrode on ITO-PEN for dye-sensitized solar cells

A novel low temperature method was used to prepare the mesoporous carbon (MC) counter electrode (CE) on indium-doped tin oxide coated polyethylene naphthalate (ITO-PEN) for flexible dye-sensitized solar cells (DSSCs). The obtained flexible MC CEs with carbon loading of 280 μg cm −2 were characterized by SEM, XRD and electrochemical impedance. The light-to-electricity conversion efficiency of the DSSC fabricated with the prepared flexible MC CE was 86% of that of DSSC based on the decomposited Pt CE.

A novel counter electrode based on mesoporous carbon for dye-sensitized solar cell

A novel carbon counter electrode for dye-sensitized solar cell was fabricated by coating the mesoporous carbon paste on fluorine-doped tin oxide glass substrate. Mesoporous carbon with pore size of 6.8 nm was distributed uniformly on the conductive substrate. The electrocatalytic activity of mesoporous carbon electrode for triiodide reduction was studied using electrochemical impedance spectroscopy. By optimizing the carbon loading and heating temperature, the charge-transfer resistance of 0.7 Ω cm 2 for mesoporous carbon counter electrode was achieved. The short-circuit current density, the open-circuit voltage, the fill factor and the over-all conversion efficiency of dye-sensitized solar cell with mesoporous carbon counter electrode were 15.5 mA cm −2, 0.605 V, 65% and 6.18%, respectively.

Application of mesoporous carbon to counter electrode for dye-sensitized solar cells

The mesoporous carbons were prepared by the carbonation of the triblock copolymer F127/phloroglucinol-formaldehyde composite self-assembled in an acid medium and employed as the catalyst for triiodide reduction in dye-sensitized solar cells (DSCs). The characteristics of mesoporous carbon were analyzed by scanning electron microscopy, transmission electron microscopy, N2 sorption measurement and X-ray diffraction. The mesoporous carbon with low crystallinity exhibited Brunauer–Emmett–Teller surface area of 400 m2 g−1, pore diameter of 6.8 nm and pore volume of 0.63 cm3 g−1. The photovoltaic performances of DSCs with mesoporous carbon counter electrode were improved by increasing the carbon loading on counter electrode due to the charge-transfer resistance of mesoporous carbon counter electrode decreasing with the increase of the carbon loading. However, further carbon loading increase has no obvious effect on the photovoltaic performance of DSCs with carbon electrode when carbon loading exceeds 300 μg cm−2. The overall conversion efficiency of 6.18% was obtained by DSCs composed of mesoporous carbon counter electrode with the carbon loading of 339 μg cm−2. This value is comparable to that of DSCs with conventional platinum counter electrode.