Nanoparticles For Dye-sensitized Solar Cells Research Articles

All-solid-state nanocomposite electrolytes composed of an ionic polymer with polar groups and surface-modified SiO2 nanoparticles for dye-sensitized solar cells

Polar groups on modified SiO2 facilitate the ionization of DMPII and enhance the efficiency of DSCs.

Polymer counter electrode of poly(3,4-ethylenedioxythiophene):Poly(4-styrenesulfonate) containing TiO2 nano-particles for dye-sensitized solar cells

A counter electrode of dye-sensitized solar cells (DSC) is an important component, which often limits the cell performance. Here we report a low-cost and high-performance polymer counter electrode of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) containing TiO2 nano-particles for dye-sensitized solar cells. Catalytic characteristics of the counter electrode are significantly improved by adding TiO2 nano-particles to PEDOT:PSS. This improvement is attributed to catalytic activation due to an increase in the surface area of the counter electrode and an increase in conductivity of PEDOT:PSS due to its structural change. A dye-sensitized solar cell using the polymer counter electrode shows 8.27% of efficiency and 16.39 mA cm−2 of short circuit current density, higher than 7.59% of efficiency and 14.75 mA cm−2 of short circuit current density of a cell with the conventional Pt counter electrode.

Counter electrode electrocatalysts from binary Pd–Co alloy nanoparticles for dye-sensitized solar cells

A class of alloyed Pd–Co catalysts are prepared by a mild solution method and subsequently blended with poly(vinylidene fluoride) (PVDF) binder for coating cost-effective counter electrodes (CEs) of dye-sensitized solar cells (DSSCs). The electrocatalytic activity for the I−/I3− redox electrolyte as well as photovoltaic performances of DSSCs are optimized by adjusting stoichiometric Pd/Co ratios. Due to the merits of resultant Pd–Co alloy CEs on good electrical conduction, rapid charge-transfer ability, and increased electrocatalytic activity, a maximum conversion efficiency of 6.44% is determined on the optimized DSSCs in comparable to 6.18% for Pt CE based DSSC. It is obvious that Pd–Co alloy CEs can be a better cost-effective and efficient alternative due to the expensive price and scarcity of Pt for the large scale applications of DSSCs.

Solar-to-Electric Performance Enhancement by Titanium Oxide Nanoparticles Coated with Porous Yttrium Oxide for Dye-Sensitized Solar Cells

TiO2–Y2O3 core–shell nanoparticles for dye-sensitized solar cells (DSSCs) have been fabricated by a solvothermal technique. The heterostructure of TiO2 nanoparticles coated with porous Y2O3 is conf...

General Strategy to Construct Hierarchical TiO2 Nanorod Arrays coupling with Plasmonic Resonance for Dye-sensitized Solar Cells

We demonstrate a general strategy to construct hierarchical TiO2 nanorod arrays (HTNRs) coupling with plasmon resonant metallic nanoparticles for dye-sensitized solar cells (DSCs). The electron transfer and interfacial recombination process have been optimized via the construction of photoanodes. Moreover, localized electric fields produced by the introduction of Au nanoparticles could excite dye molecules more effectively than the incident far-field light, resulting in further enhancement of light adsorption and photocurrent generation of DSCs. The synergistic effect of surface plasmon resonance (SPR) and constructed HTNRs has been investigated by optical spectroscopy, J-V, IPCE, EIS and OCVD measurements. An evidently improvement in energy conversion efficiency of the devices beyond 25% has been achieved via the cooperation of constructed HTNRs and SPR effects in DSCs.

Fabrication of Double Layered TiO2 Photoelectrodes Using Electrostatic Inkjet Printing

Dye-sensitized solar cells (DSSCs) are one of the most attractive electrochemical devices capable of converting light energy into electrical energy because they can be fabricated at low cost in an eco-friendly manner. Photo-electrode film of TiO2 nanoparticles in DSSC plays a major role in the light absorption and charge carrier separation and collection process. Popular fabrication methods of the photo-electrode film are screen-printing, spray-coating, spin-coating, and blade-coating. Inkjet printing of functional materials has been attracting significant attention in the light of recent attempts to manufacture various electronics such as light-emitting diodes, thin film transistors, solar cells, memory devices, sensors, biological devices, passive circuit elements, etc. However, it is well known that current inkjet printers such as thermal and piezoelectric printers cannot eject a droplet of high-viscous liquid. TiO2 paste consists of aqueous solution of TiO2 nano-particles, surfactant and polyethylene glycol, and is very high viscosity. Recently, we developed new inkjet technology, electrostatically-injected spray method. When the strong electric field was applied to a nozzle, small droplets were ejected by the electrostatic force. In this study, we apply this inkjet printing technique to develop double layered TiO2 photo-electrodes. The TiO2 paste was printed by electric field-induced inkjet printing on fluorine-doped SnO2-coated (FTO) glass electrodes and sintered at 450 °C for 30 min. DSSCs were prepared by a conventional procedure. Photovoltaic properties of each solar cell were characterized using simulated AM 1.5 sunlight illumination with an output power of 100 mW/cm2. We have successfully fabricated double layered TiO2 photo-anodes using an electrostatic inkjet printing technique. The structures and morphologies of the TiO2 film, which ultimately influence the cell performance, were controlled by changing the distance between the capillary nozzle and the FTO substrate (spraying distance). The TiO2 film formed by longer spraying distance yielded a large surface area and a highly porous structure.

Effects of cyclodextrin complexes acting as barriers on TiO2 nanoparticles in DSSCs

Abstract Dye-sensitized solar cells (DSSCs) have been the leading low-cost and clean energy conversion devices; however, their conversion efficiency still falls short of the standard set by inorganic solar cells. One method to improve the efficiency of the cell is to reduce the recombination of the injected electrons with the oxidized species of the redox couples present in the electrolytes near the surface of the bare TiO 2 particles. A model structure with a large head and a reactive group for the attachment of groups to the surface of TiO 2 has been studied to probe the size effect of additives on the performance of DSSCs. We successfully moderated the electron recombination by adding a complex composed of β-cyclodextrin and 4-methyl-1-cyclohexane carboxylic acid (MCA) to prevent the approach oxidized species toward the bare surface of the TiO 2 nanoparticles. An increase of up to 49% in the total power conversion efficiency was achieved using the β-CD–MCA complex as an additive, while only a 24% increment was obtained when small molecule additives, such as MCA, were utilized. Electrochemical impedance spectra indicated that the increase in the short-circuit current density and efficiency were observed because the surface recombination was suppressed by blocking access to the bare TiO 2 surface.

Synthesis and characterization of Nb, F-codoped titania nanoparticles for dye-sensitized solar cells

Abstract

A tri-functional TiO2photoelectrode: single crystalline nanowires directly grown on nanoparticles for dye-sensitized solar cells

We prepared a hybrid photoelectrode with single crystalline TiO2 nanowires (NWs) directly grown on TiO2 nanoparticles (NPs) for efficient dye-sensitized solar cells (DSCs). For this purpose, the NWs were grown on the commercial NPs, P25 Degussa through use of a solvothermal treatment. The NWs offer the dual functions of optical confinement and rapid electron transport, while the incorporated NPs provide a high surface area for dye loading. As a result, the NP–NW hybrid electrode showed 6.6% of the conversion efficiency under AM 1.5 illumination of 100 mW cm−2, which corresponds to a noticeable enhancement over the efficiency of the reference device with the NPs. Thus, we expect that the hybridization of two distinct nanomaterials will provide an effective strategy in designing the photoelectrode of DSCs.

Hybrid photoelectrode by using vertically aligned rutile TiO2 nanowires inlaid with anatase TiO2 nanoparticles for dye-sensitized solar cells

We report a hybrid photoelectrode fabricated by using single crystalline rutile TiO2 nanowires (NWs) inlaid with anatase TiO2 nanoparticles (NPs) for efficient dye-sensitized solar cells. For this purpose, ∼4-μm-thick vertically aligned NWs were synthesized on the FTO glass substrate through a solvothermal treatment. Then, as-prepared NW film was treated with the NP colloidal dispersion to construct the NW–NP film. In particular, the NWs offer a fast pathway for electron transport as well as light scattering effect. On the other hand, the inlaid NPs give an extra amount of space for the dye-uptake. Accordingly, the present NW–NP electrode exhibited 6.2% of the conversion efficiency, which corresponds to ∼48% improvement over the efficiency of the NP-DSC. We attribute this notable result to the synergetic effects of the enhanced light confinement, charge collection, and dye-loading.

Evaluation of Counter Electrodes Composed by Carbon Nanofibers and Nanoparticles in Dye-Sensitized Solar Cells

A series of counter electrodes (CEs) for dye-sensitized solar cells (DSSCs) was fabricated using different weight ratios of electrospun carbon nanofibers (ECNs) and carbon nanoparticles (CNPs). The conductivity of neat ECN was 838 S/m, which is more than twice than that of neat CNP, and the bulk resistance of CEs decreased as the ECN ratios increased in the composite, leading to lower transport resistance in the CEs. However, as the concentration of CNPs increased, the surface area of CEs also improved because CNPs have a much smaller dimension than ECNs, leading to higher electrocatalytic property. The CEs with higher ratio of CNPs possessed several superiorities compared with those with higher ratio ECNs, such as larger surface area for triiodide reduction, faster reaction rate, and less charge transfer resistance at the interface of CE and electrolyte. Evidenced from cyclic voltammograms and electrochemical impedance spectroscopy, the devices with higher ratio CNPs exhibited lower Nernst diffusion impedance and higher efficiency electrocatalytic performance than those with higher ratio ECNs. When the materials of CE switched from neat ECN to those with a higher concentration of CNPs, the DSSC fill factor, current density, and efficiency were improved.

Preparation of Anatase/Rutile Mixed-Phase Titania Nanoparticles for Dye-Sensitized Solar Cells

Acid-labile high surface mesoporous ZnO/Zn(OH)2 composite material is used as a novel hard template for the preparation of mesoporous amorphous TiO2. The template-free amorphous TiO2 material is then thermally crystallized at suitable temperature to control the relative ratio of anatase and rutile phases in a particle. Four different anatase/rutile (AR) mixed-phase TiO2 nanoparticles (AR-3, AR-15, AR-20, and AR-23 denoted for the samples of 3%, 15%, 20%, and 23% rutile phase, respectively) are prepared and characterized by powder X-ray diffraction (PXRD) and transmission electron microscopy (TEM). The coexistence of anatase and rutile phases in a TiO2 nanoparticle is visually confirmed by HRTEM analysis. These mixed-phase TiO2 nanoparticles are examined as candidates for photoelectrodes of dye-sensitized solar cells (DSSCs). The J-V curves and IPCE spectra for the DSSCs prepared from the mixed-phase TiO2 nanoparticles are obtained, and their photovoltaic properties are investigated. The photo-conversion efficiency (eta) indicates the highest value of 5.07% for AR-20. The synergistic effect of coexisting anatase and rutile phases with an optimal ratio in a TiO2 nanoparticle of AR-20 for an efficient interfacial transfer of photo-generated electrons is likely to lead to the highest efficiency among the AR-n samples.

Double-Layer Structure Photoanode with TiO2 Nanotubes and Nanoparticles for Dye-Sensitized Solar Cells

Here, we report a novel double-layer structure photoanode with TiO2 nanotube (TNT) layer and TiO2 nanoparticle (TP) layer via a two-step method of electrochemical anodization and screen printing for dye-sensitized solar cells (DSSCs). The results indicate that DSSCs with this double-layer structure have significant advantages of large surface area, long electron lifetime, superior electron recombination restraint characteristics, and high light scattering. The layer thickness of nanotubes and nanoparticles is also investigated and finally an optimized double-layer structure with excellent performance is prepared. With such a double-layer structure photoanode, DSSC with a relative high conversion efficiency of 6.43% and a short-circuit photocurrent density of 16.40 mA·cm−2 is obtained.

Solar Physical Vapor Deposition Preparation and Microstructural Characterization of TiO2 Based Nanophases for Dye-Sensitized Solar Cell Applications

Titanium dioxide exists in three crystalline phases: anatase, rutile and brookite. Although rutile is thermodynamically more stable, anatase is considered as the most favorable phase for photocatalysis and solar energy conversion. Recent studies have shown a significant improvement of light harvesting and overall solar conversion efficiency of anatase nanoparticles in dye-sensitized solar cells (DSSCs) when using a mixture of anatase and rutile phases (10-15% rutile). TiO2 nanopowders have been prepared by a solar physical vapor deposition process (SPVD). This method has been developed in Odeillo-Font Romeu France using "heliotron" solar reactors working under concentrated sunlight in 2 kW solar furnaces. By controlling reactor's atmosphere type (air/argon) and gas pressure, several types of anatase/rutile nanophases have been obtained with slightly different microstructural properties and morphological characteristics. X-ray diffraction analyses (XRD) were performed on precursor and on the SPVD obtained nanopowders. Information concerning their phase composition and coherence diffraction domain (crystallites size and strain) was obtained. Nanopowders morphology has been studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Rapid Synthesis of High Performance TiO2 Nanoparticles for Dye-Sensitized Solar Cells Employing Microwave and Supercritical Water

not Available.

Hybrid photoanode films based on sparse ZnO rod array-TiO2 nanoparticles in dye-sensitized solar cells

ZnO-TiO2 hybrid photoanodes were fabricated via the doctor-blade method by integrating vertically-grown sparse ZnO arrays with hydrothermal TiO2 nanoparticles. A special surface-coating technique was developed to deposit a thin TiO2 layer on the surface of ZnO rods. Microstructure, optical and photoelectrochemical performance of the hybrid photoanodes were investigated. The denser ZnO array exhibited bad filling behavior of nanoparticles in the interspace of ZnO rods, strong scattering and low conversion efficiency (0.27%). The sparser array showed a much better integrated microstructure, improved transmittance and high conversion efficiency (2.68%). The surface modification of ZnO rods by the TiO2 thin layer was found useful in improving the interfacial microstructure between the ZnO rod and the TiO2 bulk film, and the total conversion efficiency of 3.01% was achieved, higher than that of the pure TiO2 nanoparticle cell (2.93%). The increased scattering effects on the incident light, the enhanced electron transportation at TiO2/dye/electrolyte interface, and the inhabited recombination were responsible for this improvement.

Intertwined Aligned Carbon Nanotube Fiber Based Dye-Sensitized Solar Cells

Metal wires suffer from corrosion in fiber-shaped dye-sensitized solar cells (DSSCs). We report herein that stable, ultrastrong, and highly flexible aligned carbon nanotube fibers can be used not only as catalytic counter electrodes but also as conductive materials to support dye-loaded TiO(2) nanoparticles in DSSCs. The power conversion efficiency of this fiber solar cell can achieve 2.94%. These solar power fibers, exhibiting power conversion efficiency independent of incident light angle and cell length, can be woven into textiles via a convenient weaving technology.

Relationships between Cell Parameters of Dye-Sensitized Solar Cells and Dye-Adsorption Parameters

The performance of dye-sensitized solar cells (DSCs) is affected strongly by sensitizer-dye adsorption behavior on TiO(2) nanocrystal electrode. This study reports quantitative relationships between DSC cell performance parameters and dye-adsorption parameters for the first time. We discovered a logarithmic relationship between short-circuit photocurrent density (J(sc)) and dye-adsorption equilibrium constant on TiO(2) surface, and a linear relationship between open-circuit potential (V(oc)) and dye-adsorption density on TiO(2) surface for DSCs. These relationships provide a convenient method for forecasting the performance of TiO(2) nanoparticles for DSCs from the dye-adsorption parameters, and also indicate future directions for the development of high-performance TiO(2) nanoparticles for DSCs.

Vertically aligned ZnO nanorods via self-assembled spray pyrolyzed nanoparticles for dye-sensitized solar cells

Well-aligned zinc oxide (ZnO) nanorods are fabricated on indium-tin-oxide (ITO) coated glass substrates via self-assembly of ZnO nanoparticles created using continuous spray pyrolysis (CoSP) technique. The method involves pre-treatment by dip-coating the substrate with a solution comprising of zinc salt for creating a seed layer, and then spray-pyrolyzed ZnO nanoparticles self-assemble on the pre-treated substrate. The effect of the substrate pre-treatment and the deposition time (t dep ) of nanoparticles is investigated. The results show that the substrate pre-treatment influences the growth of ZnO nanorods which are absent without the pre-treatment. Nanoparticle collection and nanorod growth on different substrates are done simultaneously. The thin films of as-grown nanorods are used as photoelectrode materials to fabricate dye-sensitized solar cells (DSSCs) and the effect of nanorods grown for different times has been studied. The best performance with this cell structure is found for the layer with t dep =15 min, which showed a conversion efficiency of 1.77% for the cell area of 0.25 cm 2.

Enhanced electrocatalytic performance of graphene via incorporation of SiO2 nanoparticles for dye-sensitized solar cells

Close-packed graphene suffers from a low surface area, which limits its electrocatalytic activity as the counter electrode in dye-sensitized solar cells (DSSCs). We report herein the synthesis of a porous graphene/SiO2 nanocomposite converted from graphene oxide mixed with SiO2 nanoparticles (∼12 nm) through facile hydrazine hydrate reduction. Graphene and graphene/SiO2 films prepared by drop-casting the suspensions without organic binder or surfactant onto the conductive glass substrates at room temperature without heat treatment have been applied directly as counter electrodes in DSSCs. As compared to the nonporous graphene film, the porous graphene/SiO2 composite film demonstrates much better electrocatalytic performance for the reduction of triiodide in DSSCs due to the remarkably enhanced surface area. As a consequence, the incorporation of SiO2 nanoparticles in the graphene film improves the fill factor and power conversion efficiency by 65% and 69%, respectively. With a 2.5 μm-thick graphene/SiO2 composite film as the counter electrode, the power conversion efficiency of the DSSC achieves 6.82%, which is comparable to that for the DSSC with a Pt counter electrode.