Monolithic Dye-sensitized Solar Cells Research Articles

Iron oxide Green synthesized nanoparticles for improved performance in Monolithic Dye Sensitized Solar Cells

In order to improve photovoltaic efficiency in Monolithic Dye-Sensitized Solar Cells (MDSSCs), this study examined the effects of incorporating green produced iron oxide nanoparticles to a nanoporous carbon counter electrode. An extract from the leaves of Ocimum gratissimum was effectively used to synthesize iron oxide nanoparticles. The development of iron oxide nanoparticles was verified by optical absorption in the 350–450 nm range. With an average crystallite size of 47.9 nm, XRD patterns demonstrated the crystalline nature of the Iron oxide nanoparticles. Chemical bonds that may responsible for the nanoparticle production were found using FTIR investigations. An impressive 135.3% boost in efficiency was recorded for cell containing the Iron oxide nanoparticles, according to the MDSSC performance evaluation where DSSC without nanoparticles had a lower solar-to-electric power conversion efficiency of 1.7%, an open circuit voltage of 0.2625 V, a short-circuit current of 0.0723 mA/cm2, and a fill factor of 0.3630. The FeO CEs cell had an open-circuit voltage of 0.4274 V, a short-circuit current of 0.1042 mA/cm2, and a fill factor of 0.46. Their solar-to-electric power conversion efficiency was 4.0%. The potential of incorporating green-synthesised iron oxide nanoparticles into MDSSC counter electrode was shown by their great biocompatibility and even dispersion.

Stable Cobalt-Mediated Monolithic Dye-Sensitized Solar Cells by Full Glass Encapsulation.

Dye-sensitized solar cells (DSSCs) emerged in the market as one of the most promising indoor photovoltaic technologies to address the need for wireless powering of low-consuming electronics and sensor nodes of the internet of things (IoT). The monolithic design structure of the cell (M-DSSCs) makes the devices simpler and cheaper, and it is straightforward for constructing in-series modules. The most efficient DSSCs reported so far are Co(III/II)-mediated liquid junction cells with acetonitrile electrolytes; however, they are mostly unstable. This study reports on highly stable cobalt-mediated M-DSSCs, passing thermal cycling tests up to 85 °C according to ISOS standard protocols. Under 1000 h of aging in the dark and under simulated solar and artificial light soaking, all tested cells improved or retained their initial power conversion efficiency. Advanced long-term stability was achieved by eliminating the extrinsic factors of degradation, such as the interaction of the cell components with the environment and electrolyte leakage. This was obtained by encapsulation of the devices using a glass-frit sealant, including the holes for filling up the liquid components of the cells. The hermeticity of the encapsulation complies with the MIL-STD-883 standard fine helium gas leakage test, and its hermeticity remained unchanged after humidity-freeze cycles according to IEC 61646. The elimination of extrinsic degradation factors allowed reliable assessment of inner factors accountable for aging. The impact of the ISOS-protocol test conditions on the intrinsic device stability and long-term photovoltaic history of the M-DSSCs is discussed.

Modifications of Liquid Electrolyte for Monolithic Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSC) has been well known as a highly competitive photovoltaic technology owing to its interesting characteristics, such as, low-cost, simple, and convenient to modify both chemically and physically. One way to reduce the production cost of DSSCs is to conduct a structural modification in the form of a monolithic structure by using a single conductive substrate to accommodate both photoelectrode and counter electrode. However, the photovoltaic performance of monolithic DSSCs is typically still lacking compared to its conventional DSSCs counterparts that uses sandwich structure. One of the crucial factors that determine the photovoltaic performance of a monolithic DSSC is its electrolyte. In this work, the performance of monolithic DSSCs were studied through modifications of the electrolyte component. Two types of commercial liquid electrolytes that have different chemical properties were used and combined into various compositions, and the resulting DSSCs performances were compared. The stability of the monolithic cells was also monitored by measuring the cells repeatedly under the same condition. The result showed that during the first measurement the highest performance with a power conversion efficiency of 1.69% was achieved by the cell with a higher viscosity electrolyte. Meanwhile, the most stable performance is shown by the cell containing lower viscosity electrolyte, which achieved an efficiency of 0.66% that measured on day 35.

Influence of Inorganic Binder Composition on the Structure-Property Relationship of Monolithic Dye-sensitized Solar Cells with Carbon-based Counter Electrode

In order to fabricate a low-cost dye-sensitized solar cell (DSSC), carbon has become a highly preferred catalytic material as counter-electrode, particularly for DSSC with monolithic structure. This paper presents novel synthesis method of carbon-based composite pastes using two types of carbon material, i.e. carbon nanopowder and activated carbon. The concentrations of the inorganic binder added to the composite pastes were varied to investigate their effect on the physical properties of the counter electrode and the electronic properties of the constructed monolithic DSSC. The inorganic binder used in this work was titanium dioxide nanoparticles, Evonik P25. After optimization, power conversion efficiency of 0.221% was achieved by the monolithic DSSC with counter electrode composite comprising activated carbon and titanium dioxide with weight concentration of 0.5 g and 0.25 g, respectively. Characterizations using gas sorption technique showed that the shape of the hysteresis curves obtained for all composites resembled the isotherm curve Type II and H3, indicating the presence of micropores. Furthermore, higher concentration of titanium dioxide nanoparticles as binder led to counter electrode with lower surface area. The solar cell efficiency, however, was found to be not only correlated to the surface area or the binder composition, but it was also determined by the type of the carbon material.

Development of monolithic dye sensitized solar cell fabrication with polymer-based counter electrode

Fabrication of monolithic dye sensitized solar cell (DSSC) has been developed by using a poly(3,4 ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) polymer as counter electrode. The number of layers and annealing temperature of PEDOT:PSS layers which is prepared by screen printing technique has been investigated to find the optimum performance of monolithic DSSC. The best performance of monolithic DSSC with 0.61 V open circuit voltage, 1.26 mA short circuits current, and 1.77% efficiency were resulted in 3 layers of PEDOT: PSS with annealing temperature at 120°C. The conductivity of counter electrode layer increase with the increasing of number of polymer layer, produce a high short circuit current. Otherwise, increasing the annealing temperature of PEDOT:PSS layer increases the conductivity of counter electrode layer, but decreases the Isc value.

The influence of carbon counter electrode composition on the performance of monolithic dye-sensitized solar cells

In this research, the influence of carbon composition on the physical and electrical characteristics of the counter electrode and the performance of monolithic dye-sensitized solar cell (DSSC) was investigated. Screen printing method was used due to its excellence such as simple fabrication process at mass production. Physical and electrical characterization of the counter electrode layer were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, gas sorption using Brunauer-Emmett-Teller (BET) method, and four-point probe measurement. Meanwhile, the DSSC performance was characterized using current-voltage (I-V) and incident photon-to-current efficiency (IPCE) measurement system. It is found that the carbon composition affects the physical and electrical characteristics of the counter electrode, such as the porosity, crystallinity, BET surface area, and micro-sized agglomeration. However, relatively similar conductivity values are obtained regardless of the carbon composition. The results show that the composition of graphite and active carbon with a ratio of 1:4 as a counter electrode material produced a porous layer with approximately 3.32 μm of agglomerates and conductivity with a sheet resistance value of 11.60 Ω/sq that overall can improve the performance of the monolithic DSSC. The highest efficiency obtained is 1.52% and the highest QE value is 32% at the absorption area of TiO2, with Voc, Isc and Pmax value of 0.63 V, 1.19 mA and 0.91 mW, respectively.

Development of Lower Cost Monolithic Dye-Sensitized Solar Cell with Carbon Counter-Electrode

Dye-sensitized solar cells (DSSCs) were developed as low-cost and environmentally friendly alternatives to other types of solar cells. However, due to efficiency and stability shortcomings, and also because of the cost reductions in crystalline Si cells, DSSCs are not yet commercially successful. Several parameters have to be improved, one of which is the cost that should be reduced further. There are two ideas to achieve this: the platinum electrode can be substituted by a cheaper carbon electrode, and the sandwich structure of the cells, with two glass substrates with a transparent conducting oxide (TCO) layer on them, can be changed to a monolithic structure, in which only one TCO-coated glass substrate is used. In the present project the performance of such monolithic cells with carbon counter-electrode is compared to the performance of cells with sandwich structure that are otherwise identically constructed. The performance assessment was done by means of an I-V curve measurement. The main result is that monolithic cells have a lower efficiency. The data indicate that the internal serial resistance of the monolithic cells was higher than in the sandwich cells. In a further step, three monolithic cells were interconnected in series in a submodule, and the performance of this submodule was assessed. The result indicates that the serial resistance of the three cells that were interconnected in the submodule, including the contacts, was lower than three times the serial resistance of the individual cells including the contacts. This shows that there is a potential for a more efficient usage of monolithic cells by means of a module design that allows for lower resistances in the interconnection of the cells within the module as well as in the module contacts. This should be pursued in further research, as well as the reduction of the internal resistance of the monolithic cells.

A Comparison of the Utilization of Carbon Nanopowder and Activated Carbon as Counter Electrode for Monolithic Dye-Sensitized Solar Cells (DSSC)

Monolithic design is one of the most promising dye-sensitized solar cell (DSSC) architectures to develop, because it allows the elimination of one conductive substrate and offers the possibility for printing layer-by-layer of the materials that made up its structure. In this study, titanium dioxide-based monolithic type DSSCs were fabricated on a single fluorine-doped transparent oxide coated glass with TiO2 as photoanode and porous ZrO2 as spacer. The type of the carbon material used as the composite paste for the counter electrode was varied to see the effect on the solar cell efficiency. Four-point probes measurement revealed that the resistivity of the carbon layer synthesized using activated carbon exhibited slightly higher conductivity with a sheet resistance of 10.70 Ω/sq and 11.09 Ω/sq for activated carbon and carbon nanopowder, respectively. The efficiency of DSSC that uses activated carbon as counter electrode was higher (i.e. 0.221%) than the DSSC with carbon nanopowder (i.e. 0.005%). The better performance of DSSC with activated carbon as a counter electrode was due to its better conductivity and higher surface area compared to those of carbon nanopowder.

Analysis of Thermal Treatment Zirconia as Spacer Layer on Dye-Sensitized Solar Cell (DSSC) Performance with Monolithic Structure

Monolithic dye-sensitized solar cells (DSSC) offer the prospect of lower material cost and require a simpler manufacturing process compared with conventional DSSC. Fabricated on a single fluorine tin oxide (FTO) glass substrate consists of a nanoporous TiO2 photoanode layer, a ZrO2 spacer layer, a carbon counter electrode layer, a dye, and an electrolyte. The spacer layer on the monolithic DSSC serves as electrolyte storage and insulating layer to separate between photoanode and counter electrode. Zirconia is often used as a spacer because it has high temperature resistant properties, high dielectric constant and adhesive as an insulator that has band gap between 5-6 eV. The effects of the thermal treatment of zirconia layer as a spacer electrolyte on the performance of monolithic DSSC have been investigated. The cell’s performance increases with the sintering temperature as well as indicated by the decreased in particle size and increased in quantum efficiency in the absorption region of the titania layer. Co-sintering treatment tends to drastically reduce cell’s performance. The highest performance was obtained at a temperature sintering of 500o C with an PCE of 0.22%, Isc = 0.16 mA and Voc = 0.71 V.

Monolithic dye sensitized solar cell with metal foil counter electrode

Abstract Monolithic dye-sensitized solar cells are conventionally fabricated using carbon composite layer as the counter electrode. In the current research, the brittle carbon composite layer is replaced with a metal foil, aiming to decrease the device series resistance and using less catalyst material in counter electrode. This metallic structure has also an advantage of mechanical strength and decreases the fabrication complexity. The counter electrode is prepared by electrodepositing Cr film followed by electrodepositing Pt nanoparticles on a metal foil. As the porous spacer layer, different composite layers of SiO2, TiO2, and Al2O3 are investigated and the best results are obtained for TiO2 (rutile)@SiO2 with average particle size of 300 nm, duo to the high refractive index of rutile TiO2 nanoparticles and good insulating properties of the shells. The best efficiency of 9.5% (8.0% with mask) is achieved with 20 cycles of Pt deposition and spacer layer fabricated by TiO2 (rutile)@SiO2 particles.

Analysis of Catalytic Material Effect on the Photovoltaic Properties of Monolithic Dye-sensitized Solar Cells

Dye-sensitized solar cells (DSSC) are widely developed due to their attractive appearance and simple fabrication processes. One of the challenges that arise in the DSSC fabrication involves high material cost associated with the cost of conductive substrate. DSSC with monolithic configuration was then developed on the basis of this motivation. In this contribution, titanium dioxide-based monolithic type DSSCs were fabricated on a single fluorine-doped transparent oxide coated glass using porous ZrO2 as spacer. Herein, the catalytic material for the counter-electrode was varied using carbon composite and platinum in order to analyze their effect on the solar cell efficiency. Four-point probe measurement revealed that the carbon composite exhibited slightly higher conductivity with a sheet resistance of 9.8 Ω/sq and 10.9 Ω/sq for carbon and platinum, respectively. Likewise, the photoconversion efficiency of the monolithic cells with carbon counter-electrode almost doubled the efficiency of the cells with platinum counter-electrode. Our results demonstrate that carbon could outperform the performance of platinum as catalytic material in monolithic DSSC.

Multi-layered hierarchical nanostructures for transparent monolithic dye-sensitized solar cell architectures

Monolithic dye-sensitized solar cell (DSC) architectures hold great potential for building-integrated photovoltaics applications. They indeed benefit from lower weight and manufacturing costs as they avoid the use of a transparent conductive oxide (TCO)-coated glass counter electrode. In this work, a transparent monolithic DSC comprising a hierarchical 1D nanostructure stack is fabricated by physical vapor deposition techniques. The proof of concept device comprises hyperbranched TiO2 nanostructures, sensitized by the prototypical N719, as photoanode, a hierarchical nanoporous Al2O3 spacer, and a microporous indium tin oxide (ITO) top electrode. An overall 3.12% power conversion efficiency with 60% transmittance outside the dye absorption spectral window is demonstrated. The introduction of a porous TCO layer allows an efficient trade-off between transparency and power conversion. The porous ITO exhibits submicrometer voids and supports annealing temperatures above 400 °C without compromising its optoelectronical properties. After thermal annealing at 500 °C, the resistivity, mobility, and carrier concentration of the 800 nm-thick porous ITO layer are found to be respectively 2.3 × 10−3 Ω cm−1, 11 cm2 V−1 s−1, and 1.62 × 1020 cm−3, resulting in a series resistance in the complete device architecture of 45 Ω. Electrochemical impedance and intensity-modulated photocurrent/photovoltage spectroscopy give insight into the electronic charge dynamic within the hierarchical monolithic DSCs, paving the way for potential device architecture improvements.

Vertically-oriented few-layer graphene supported by silicon microchannel plates as a counter electrode in dye-sensitized solar cells

Vertically-oriented few-layer graphene supported by silicon microchannel plates annealed at different temperatures are used in dye-sensitized solar cells (DSSCs). The structure, morphology, and electrochemical characteristics are determined by AFM, SEM, XPS, cyclic voltammetry, electrochemical impedance spectroscopy, and photocurrent density-voltage curves. The graphene/Si-MCP fabricated by electrochemical exfoliation delivers enhanced power conversion efficiency in DSSC and the materials annealed under ambient conditions at 300 °C show the best results due to the smaller oxygen concentration in graphene and larger electrical conductance. Owing to the microelectronics-compatible fabrication process and excellent properties of the device, the counter electrode has large potential in high-performance silicon-based monolithic DSSCs.

Application of highly reflective spacer layer in monolithic dye-sensitized solar cells

Monolithic dye-sensitized solar cells (DSSCs) based on TiO2/spacer/carbon triple mesoporous films are low-cost, ease of fabrication with screen printing technology, possessing great potential to produce electricity from sunlight. The power conversion efficiency is still low compared to commercial photovoltaic technology. For DSSCs with platinum coated FTO or gold as counter electrode, the mirror like surface of counter electrode can reflect visible light back to be re-absorbed by dye-sensitized TiO2 film. However, for monolithic DSSCs, there is no reflection layer. To enhance absorbance of incident photons is an important way to improve photocurrent of monolithic DSSCs. Spacer film can be used as scattering layer to reflect visible light. However, spacer usually absorbs large amount of dyes due to large surface area and surface basic sites. Here, we report highly reflective spacer with no dyes anchoring onto surfaces of spacer. The scattering centers are sub-micrometer voids created by decomposing sub-micrometer polystyrene (PS) spheres. The building blocks are composed of rutile TiO2@SiO2. Rutile TiO2 was selected due to its large refractive index. SiO2 was coated on surface of rutile TiO2 to avoid dye adsorption. Moreover, the sub-micrometer voids provide fast transporting channels for redox species. To fabricate spacer paste that can be used with screen printing method to produce film, rutile TiO2@SiO2 nanoparticles and PS spheres with diameter of 400nm were first synthesized separately and then, they were mixed homogeneously by ball milling with addition of ethyl cellulose binder and organic dispersant medium (α-terpineol). Rutile TiO2 was obtained by reaction of TiCl4 in HCl aqueous solution at 80°C and sub-micrometer PS spheres were synthesized with emulsion polymerization of styrene monomer at 70°C. Rutile TiO2@SiO2 core@shell nanoparticles were obtained by hydrolysis of tetraethyl silicate on the surface of rutile TiO2. The UV-visible reflection spectra of sintered spacer film at 500°C showed that the spacer film with ratio (rutile TiO2@SiO2 to polystyrene) of 1:0.2 or 1:0.4 have maximum reflectivity in the visible range. However, the conventional ZrO2 spacer film with the same thickness has much weaker reflectivity. The dye absorption test of bilayer film with spacer lying top of TiO2 film reveals that the dye molecules can easily go through spacer film to absorb onto surface of mesoporous TiO2 film while the spacer film on the top keeps white color unchanged. Scanning electron images of spacer film also showed that sub-micrometer voids distributed uniformly in the film and the diameter of voids is similar to that of PS spheres. These sub-micrometer voids in spacer film can provide fast transporting channels for redox species, facilitating dye regeneration. By replacing the conventional ZrO2 spacer with the advanced spacer, photocurrent density of monolithic DSSCs was increased by 25%. As a result, the power conversion efficiency has been improved to 4.61% from 3.95% with non-volatile iodine-free polymer gel electrolyte. These results endow spacer a new ability in the device and provide another guideline to enhance photocurrent of monolithic dye-sensitized solar cells. The design of spacer in this work may find other applications in the area of optics, catalyst, etc.

Carbon nanotubes hybrid carbon counter electrode for high efficiency dye-sensitized solar cells

We report a solution-based method to prepare a hybrid carbon materials consisted of carbon nanotubes modified graphite/carbon black as a low-cost platinum-free counter electrode for dye-sensitized solar cell (DSSC). The effects of carbon nanotube content on the performance of counter electrode are examined. The 25 wt% carbon nanotubes in carbon counter electrode exhibit high catalytic activity for the reduction of triiodide to iodide and low charge transfer resistance at the electrolyte–electrode interface. The DSSC based on this counter electrode achieves a high power conversion efficiency of 6.94 % under 100 mW cm−2 illumination (AM 1.5), which is comparable to 7.06 % for the DSSC with Pt counter electrode. It is expected that this low cost hybrid carbon counter electrode with simple manufacturing process would make the carbon catalyst-based monolithic DSSC more efficient in practical application.

Fabrication and Performances of Flexible Monolithic Dye-sensitized Solar Cell Using Metal Reinforced Porous Counter Electrodes

We report here the world’s first large size plastic monolithic dye-sensitized solar cells (DSCs) with size of 1cmx10cm. A novel printable metal-carbon/graphite composite was used as the counter electrode. By transferring this counter electrode on top of working electrode through a cold isostatic pressing technology, flexible monolithic DSC was successfully fabricated. Our results show that charge transfer resistance of carbon/graphite counter electrode was reduced to about 0.2 Ω.cm2 after being reinforced with magnetron sputtering coated Pt nano particles, which is comparable with sandwich structure plastic DSC with commercial Pt/ITO-PET substrates. Keywords: Cold isostatic pressing, flexible monolithic dye-sensitized solar cell, magnetron sputter coating, metal reinforced carbon/graphite composites.

Push–pull porphyrins with different anchoring group orientations for fully printable monolithic dye-sensitized solar cells with mesoscopic carbon counter electrodes

Compared with WH-C4 and WH-C1, WH-C6- and WH-C7-sensitized devices show a significantly reduced Voc, Jsc and power conversion efficiency (η).

Structure and photoelectrochemical properties of silicon microstructures arrays

Two silicon microstructrues of silicon nanowires (SiNWs) and silicon microchannel plates (Si MCP) have been successfully fabricated combined by standard microelectronics technology and electrochemical method. The performances have been investigated for dye-sensitized solar cells (DSSCs) by applying silicon nanowires (SiNWs) and silicon microchannel plates (Si MCP) to the counter electrode, respectively. And the electrocatalytic activities of Si MCP and SiNWs electrodes for triiodide reduction were studied using electrochemical impedance spectroscopy. The two microstructure electrodes consisting of a large number of channels with high surface to volume ratio exhibits a highly interconnected network structure with good catalytic activity. A high photovolatic conversion efficiency of over 7.01% and 7.86% were recorded for DSSCs based on the Si MCP and SiNWs counter electrodes, which is comparatable to the cell based on conventional Pt counter electrode at the same condition. It could be expected that this low cost SiNWs and Si MCP and compatibility with microelectronic technology would make the silicon-based monolithic DSSC available in practical application.

Fabrication of Spacer and Catalytic Layers in Monolithic Dye-Sensitized Solar Cells

Over the past few years, dye-sensitized solar cell (DSC) research has been focused on the material and process cost reduction, and on the electronics integration of the devices. Monolithic design is one of the most promising DSC architectures for mass production, because it allows the elimination of one conductive substrate and offers the possibility of printing layer-by-layer the materials that compose the structure. In this study, the formulation, the realization, and the processing of the spacer and the catalyst layers are proposed, and the relative performance in terms of J-V characteristics, incident photon to current conversion efficiency, and impedance analysis of the device with the optimized material thickness is reported. The optimized profile of the overall structure permits us to obtain masked cells with a conversion efficiency of about 5% with no chemical treatment.

Highly Efficient Monolithic Dye-Sensitized Solar Cells

Monolithic dye-sensitized solar cells (M-DSSCs) provide an effective way to reduce the fabrication cost of general DSSCs since they do not require transparent conducting oxide substrates for the counter electrode. However, conventional monolithic devices have low efficiency because of the impediments resulting from counter electrode materials and spacer layers. Here, we demonstrate highly efficient M-DSSCs featuring a highly conductive polymer combined with macroporous polymer spacer layers. With M-DSSCs based on a PEDOT/polymer spacer layer, a power conversion efficiency of 7.73% was achieved, which is, to the best of our knowledge, the highest efficiency for M-DSSCs to date. Further, PEDOT/polymer spacer layers were applied to flexible DSSCs and their cell performance was investigated.