Photoanodes For Dye-sensitized Solar Cells Research Articles

Chemically tuned, bi-functional polar interlayer for TiO2 photoanodes in fibre-shaped dye-sensitized solar cells

A polar interlayer is introduced to TiO2 photoanodes as a novel strategy to improve the performance of fibre-shaped dye-sensitized solar cells.

Applications of Factorial Design in Dye-Sensitized Solar Cells with Titanium-Silicon Dioxide as Photoanode

Titanium-silicon dioxide (TiO2-SiO2) nanocomposite thin films have been synthesized by sol-gel process as a photoanode in dye-sensitized solar cells (DSSC). The photovoltaic performances, i.e. JSC, VOC, FF, and η were explored using I–V measurement. The effects of electrolyte type (iodolyte, PAN-based gel polymer: E1 and E2) and the preparation of photoanode (annealed temperature) on the performance of DSSC was significantly studied using factorial design methodology. It reveals that in factorial design, both main factors (electrolyte type and annealed temperature) and the interaction between these two factors were found statistically significant. It means that the effects of electrolyte type and annealed temperature, are the significant variables influencing the energy efficiency, as well as the two-factor interactions of electrolyte type and annealed temperature. The determination coefficient (R2) also in good alliance, which confirms that there exist a high association between these factors with the energy efficiency of DSSC. The optimum conditions of the energy efficiency occurs for a PAN-based gel polymer E2 when the photoanode was annealed at 350C, exhibits a highest energy efficiency of 1.5%.

Dyes Amount and Light Scattering Influence on the Photocurrent Enhancement of Titanium Dioxide Hierarchically Structured Photoanodes for Dye-Sensitized Solar Cells

In this study, we prepared and analyzed the properties of hill-like hierarchically structured titanium dioxide (TiO2) photoanodes for dye-sensitized solar cells (DSSCs). We expected that the presence of appropriately aggregated TiO2 clusters in the photoanode layer would translate to relatively strong light scattering and dye loading, increasing the photovoltaic efficiency. A detailed light-harvesting study was performed by employing polyvinyl alcohol (PVA) polymers of different molecular weights as binders for the aggregation of the TiO2 nanoparticles (P-25 Degussa). Hence, we obtained a series of TiO2 films, presenting a variety of morphologies. Their reflection, as well as absorbance of light by the attached dye, the amount of dye loading, and the performance of the fabricated DSSC devices were investigated. Our optimized device, with a relatively high dye loading and good light harvesting ability, was able to enhance the short-circuit current (Jsc) in the DSSCs by 23%.

Apparatus-dependent sol-gel synthesis of TiO2 nanoparticles for dye-sensitized solar cells

Synthesis of titanium dioxide nanoparticles (TiO2 NPs) has been done by sol-gel-hydrothermal colloidal route in two different apparatus; one being simple stainless steel (named as TiO2-B) and other being at constant temperature and pressure autoclave (named as TiO2-W). These TiO2 NPs were investigated by various characterization techniques such as scanning electron microscope (SEM), X-ray diffractometer (XRD), and photoluminescence spectrophotometer. Also, it was observed that the quality of the synthesized TiO2-W NPs is comparable with the commercial TiO2 NPs (TiO2-C), whereas the cost of synthesis is almost reduced to half. The synthesized TiO2 NPs are used as the photoanode in dye-sensitized solar cell (DSSC). DSSC with TiO2-W showed better power conversion efficiency as compared to DSSC with TiO2-B.

Synthesis of Flower-Like ZnO Micro/Nano Structures by the Spray Pyrolysis Technique

Flower-like zinc oxide (ZnO) micro-/nano-structures are synthesized as thin films on glass substrates by the spray pyrolysis technique at a substrate temperature of 350 ± 5°C. The films are characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) and x-ray energy dispersion spectroscopy (EDS). Absorbance spectra (UV–Vis) and ImageJ software is used for size analysis. The XRD diffractogram revealed that the films have a hexagonal (wurtzite) phase with preferential orientation along the (002) line. SEM images showed that the films have a micro/nano flower-like structure. EDS spectra revealed that the films contain chlorine in addition to zinc and oxygen. Absorbance measurements were used to estimate the band gap energies, which were found to be larger than the bulk value. Such morphologies and band gap values are advantageous when using ZnO as fore contact and/or window material in thin-film solar cells and photoanodes in dye-sensitized solar cells, optoelectronic devices and gas sensors.

Photovoltaic Properties of an rGO/Pt Counter Electrode With AZO Photoanode for Dye-Sensitized Solar Cells Under Low Light Intensity

This study used reduced graphene oxide (rGO) applied to a platinum (Pt) counter electrode to improve light conversion efficiency. The study also used an Al-doped Zinc Oxide (AZO) nanosheet/TiO2 photoanode for the dye-sensitized solar cell (DSSC). Photovoltaic characteristics, electrochemical impedance spectroscopy (EIS), field-emission scanning electron microscopy (FE-SEM) and Raman spectroscopy were used to analyze DSSC. The different light intensities and photovoltaic characteristics were analyzed to determine optimal light intensity conditions. The unmodified Pt counter electrode was compared with the rGO/Pt counter electrode, photovoltaic conversion efficiency ( ${\eta }$ ) increased from 3.60% to 4.04% due to the rGO modification as it possesses a higher specific surface area. Its low cost also makes it suitable for mass production. In addition, an AZO nanosheet/TiO2 photoanode was fabricated to form a double-layer structure in which photovoltaic conversion efficiency was 4.47 %. Finally, a DSSC with an AZO/TiO2 photoanode and rGO/Pt counter electrode was fabricated and had an photovoltaic conversion efficiency of 5.05 %. This study also analyzed the photovoltaic parameters of DSSC under different light intensities, which shows the optimal photovoltaic conversion efficiency of 5.54% under 30mW/cm2.

Correction to “Synthesis of TiO2 Nanoparticles on Plasma-Treated Carbon Nanotubes and Its Application in Photoanodes of Dye-Sensitized Solar Cells”

Correction to “Synthesis of TiO₂ Nanoparticles on Plasma-Treated Carbon Nanotubes and Its Application in Photoanodes of Dye-Sensitized Solar Cells”

Sol–gel approach for the growth of vertically aligned 3D-TiO2 nanorod arrays as an efficient photoanode for high-performance dye-sensitized solar cells

In this study, a facile, low cost, and scalable sol–gel method has been proposed for the coating of ultra-thin layer of TiO2 on FTO substrate as a seed layer for the growth of 3D-TiO2 nanorod (3D-TiO2-NR) arrays on FTO. Then, the two-step hydrothermal process including nanorod growth and the chemical etching treatment was proceeded for the fabrication of FTO/3D-TiO2-NR photoanodes. The thickness of the deposited TiO2 in FTO/TiO2-sg samples was measured with small-angle X-ray scattering technique, and it was obtained to be 21.3 nm. FE-SEM and TEM techniques were used for the morphological characterization of 3D-TiO2-NR, and it was obtained that the tightly adhered film of vertically aligned 3D-TiO2-NR with two-layer nanostructuring is formed with a cubic base and a nanorods head. Finally, DSSCs with iodine-based and cobalt(II/III) tris(2,2′-bipyridine) complex-based electrolytes with two different photoanodes including 3D-TiO2-NR and TiO2-NP were assembled and their photovoltaic characteristics were investigated. For [Co(bpy)3]2+/3+ shuttle-based DSSC, the obtained power conversion efficiency (η) was about 3.5% with Jsc of 9.36 mA cm−2 in 3D-TiO2-NR-based DSSC, while η of TiO2-NP-based DSSC was about 1.4%. The results showed that employing 3D-TiO2-NR-based photoanode in DSSCs with bulky electron shuttles remarkably improves the photovoltaic characteristics of DSSCs. Electrochemical impedance spectroscopic studies also showed the lower charge transfer resistances for DSSCs with nanorod-based photoanode building blocks.

Fabrication of Titanium Dioxide-reduced Graphene Oxide (TiO2/rGO) nanocomposites as the Photoanode in Dye Sensitized Solar Cells

One of the photovoltaic cells generation promising for low-cost fabrication is dye-sensitized solar cell (DSSC). However, it has a drawback─low efficiency because of electron recombination occurrence and low transparency of photoanode. Graphene-based materials show the potential to overcome this problem. In this work, we have investigated the integration of reduced graphene oxide (rGO) into the titanium dioxide (TiO2) photoanode in DSSC. A simple Hummer’s method has been used to synthesize graphene oxide flakes. The nanocomposite of rGO/TiO2 has been formed by varying the percentage of rGO between 1% and 5%. The result shows that the percentage of rGO in nanocomposite affected device performance. The efficiency decreases along with the increase in rGO. The best result was obtained with 2 wt% addition of rGO into TiO2 photoanode that resulted in 0.9 % efficiency.

Fabrication of TiO2 nanoparticle/TiO2 microcone array photoanode for fiber-type dye-sensitized solar cells: Effect of acid concentration on morphology of microcone

Fiber-type dye-sensitized solar cell (FDSSC) is one of the promising energy generating devices for soft electronics, especially due to the great photon-to-electricity conversion ability even under weak deem light. High dye adsorption, great light utilization, efficient charger-transfer routes and excellent flexibility are required for the photoanode of FDSSCs. In this study, flexible Ti wires are etched using different concentrations of H2SO4 electrolytes in anodization process to form TiO2 microcone array (TMC) as the photoanode of FDSSCs at the first time. Growth mechanism of TMC in different concentrations of H2SO4 electrolytes is proposed to more clearly explain the acid concentration effects. The FDSSC with the TMC photoanode prepared using 4 M H2SO4 electrolyte shows the highest photon-to-electricity conversion efficiency (η) of 2.11%, due to the formation of well-distributed TMC to provide one-dimensional charge-transfer paths and induce effective light scattering. The TiO2 nanoparticle (TNP) is deposited on TMC using dip-coating technique. The η is enhanced to 3.70% for the FDSSC with the optimized TNP thickness, which is able to provide sufficient surface area for dye adsorption and prevent the thickness from exceeding charge diffusion length. Electrochemical impedance spectroscopy is used to analyze the charge-transfer resistance of FDSSCs with the fancy TNP/TMC photoanodes.

Complementary properties of silver nanoparticles on the photovoltaic performance of titania nanospheres based photoanode in dye-sensitized solar cells

In this study, the fabrication of photoanode of dye-sensitized solar cell using silver@titania nanospheres and N719 dye, and its enhanced photovoltaic performance in the dye-sensitized solar cell is described. Silver@titania with different mol. % of silver (1, 3 and 5 %) are synthesized using facile sol-gel and photochemical reduction method and are characterized by suitable analytical techniques. The synthesized nanocomposite materials showed nanospheres like morphology. Moreover, the photoluminescence studies revealed that incorporation of silver nanoparticles on the titania nanospheres surface suppressed the charge recombination process and which is more beneficial for dye-sensitized solar cells. Silver@titania nanospheres are successfully employed as a photoanode and demonstrated with an enhanced solar-to-electrical energy conversion efficiency of 5.24 %, under full sun illumination (100 mW cm−2, AM 1.5G) which is 30.67 % enhancement than that of bare titania nanospheres (4.01 %). This enhanced efficiency is attributed to the rapid interfacial charge transfer process and plasmonic effect offered by silver nanoparticles present in the silver@titania nanospheres. The improved charge transfer process led to minimize the back electron transfer reaction in the device. With complementary properties of silver nanoparticles, the high performance demonstrated by the silver@titania nanospheres could be an excellent candidate for the light energy harvesting applications.

Preparation, Characterization and Photosensitizing Activities of Homoleptic Cu(II) Dithiocarbamates in TiO2‐Based DSSC

AbstractNew homoleptic copper(II) dithiocarbamate complexes, [Cu(L1‐L5)2] (L1=N‐benzyl‐N‐4‐bromobenzyl dithiocarbamate− Cu1; L2=N‐benzyl‐N‐4‐methoxybenzyl dithiocarbamate− Cu2; L3=4‐N,N‐diethylbenzyl‐N‐methyl dithiocarbamate− Cu3; L4=N‐methyl‐N‐4‐isopropylbenzyl dithiocarbamate− Cu4 and L5=N‐3‐pyridyl‐N‐4‐bromobenzyl dithiocarbamate− Cu5) have been synthesized and characterized by elemental analysis, HRMS, IR and UV‐Vis. spectroscopy, PXRD and cyclic voltammetry. The monomeric (1−3) and dimeric (4) structures have been elucidated by X‐ray crystallography. In all four structures the copper atom has square planar geometry. In 3 and 4 existence of rare C−H⋅⋅⋅Cu intermolecular anagostic interactions have been detected in the solid state. All complexes were exploited as sensitizers for TiO2 photoanode based dye‐sensitized solar cells (DSSC). When TiO2 anchored with these complexes was used as DSSC photoanode, significant light harvesting properties were observed with an exceptionally high light‐to‐electrical energy conversion efficiency (3.62%) shown by Cu3 complex. The extent of interfacial charge‐recombination and electron lifetime was evaluated from the electrochemical impedance spectroscopy (EIS) studies. The better performance of Cu3 compared to other complexes was attributed to its structural features. All the complexes with σrt, 10−6‐10−9 S cm−1 are weakly conducting but show semiconducting behaviour in the 303–383 K temperature range with Ea values of 0.20−0.90 eV.

RGO based photo-anode in dye-sensitized solar cells (DSSC) and its photovoltaic characteristics

On the attempt to increase transport properties of the photo-anode in DSSC, we synthesized rGO powder from graphite bar (commercially available) using modified Hummer’s method. The SEM-EDS results had confirmed the attachment of the rGO layer to the FTO substrate. For DSSC cells, we made two cells configuration, the first one was stacking layers of rGO and TiO2 resulting configuration of TiO2/rGO/TiO2 (A2) and rGO/TiO2/rGO (A3), where rGO was deposited by spin coating and TiO2 was deposited by a screen printing technique. The second one, the rGO powder was mixed with TiO2 paste with several ratios in weight, namely TiO2:rGO 40:1 (B1), 40:2 (B2), and 40:8 (B3) and then deposited on the FTO substrate by screen printing. The reference cell was assigned as A1 (TiO2 only). From the conductivity measurement using the four-probe method, the utilization of rGO layer increased the conductivity of photoanode layer, namely (1.37, 2.9 and 6.3)x10−2 Ω−1cm−1 for A1 to A3 and (1.5, 2.5, and 3.7)x10−2 Ω−1cm−1 for B1 to B3. From the photovoltaic measurement, we found that the efficiency of the DSSC cell firstly increased with the insertion of rGO layer, from 1.8% (A1) to 4.59% (A2), and decreased to 3.22%, as the conductivity increased in A3. While for the composite of TiO2:rGO, the efficiency of the cell reduced with the increased amount of rGO, from 3.45% (B1) to 2.9% and 1.9% for B2 and B3. We found that the reduction of photovoltaic performance was affected by two main factors, specifically, direct contact between rGO and redox species in the electrolyte, which induced recombination process, and conductivity of the photo-anode layer. To fully achieve the advantage of rGO utilization in photo-anode, once must be considered was the use of protection layer on top of the rGO layer to avoid direct contact between the rGO/electrolyte interface.

TiO2 Coated ZnO Nanorods by Mist Chemical Vapor Deposition for Application as Photoanodes for Dye-Sensitized Solar Cells.

In this study, a mist chemical vapor deposition method was applied to create a coating of titanium dioxide particles in order to fabricate ZnO/TiO2 core–shell nanostructures. The thin layers of titanium dioxide on the zinc oxide nanorods were uniform and confirmed as pure anatase phase. The morphological, structural, optical and photoluminescence properties of the ZnO/TiO2 core–shell structures were influenced by coating time. For instance, the crystallinity of the titanium dioxide increased in accordance with an increase in the duration of the coating time. Additionally, the thickness of the titanium dioxide layer gradually increased with the coating time, resulting in an increased surface area. The transmittance of the arrayed ZnO/TiO2 core–shell structures was 65% after 15 min of coating. The obtained ZnO/TiO2 core–shell nanostructures demonstrated high potentiality to serve as photoanodes for application in dye-sensitized solar cells.

(Invited) Challenges and Opportunities in Dye Sensitized Solar Cells Using DBD Plasma Treated Upconversion Nanoparticles

1. Introduction The dye-sensitized solar cells(DSSC) are widely receiving increasing attention as low-cost solar cells. The photoelectrode of the DSSC is composed of a nanoporous TiO2film which has a very large specific area, on which a sensitizing dye is adsorbed [1]. The specific chemical composition, surface area and surface profiles of the TiO2films determine the energy conversion efficiency of the DSSCs. Through surface treatment, these properties of TiO2can be enhanced [2]. DSSCs generally use visible light for photo-electric conversion. In a DSSC, light absorption is conducted by a light sensitive dye. The ability of the dye to capture light in a wide band range of the light spectrum determines the conversion efficiency of the DSSC. The currently employed dyes in DSSC with the highest conversion efficiencies (N-719) have a light spectrum absorption range of 300-750 nm [1]. Consequently, the inability of these dyes to absorb near infrared (NIR) light, which makes up to 48% of energy of the entire solar spectrum, forms the main energy loss mechanism of DSSC. To realize photo-current conversion from these light, rare-earth luminescent phosphors, which have large band gap, high refractive index, low phonon energy are promising to circumvent the photon transmission losses [2]. 2. Experimental details 2.1 Sample preparation A facile urea based homogeneous precipitation method was employed for the fabrication of Y2O3:Er3+/Yb3+nanoparticles. DSSC was fabricated via the conventional doctor blade method. For the preparation of the DSSC photoanode, transparent TiO2 colloids were deposited on the conductive glass substrate (FTO) to form a transparent photoelectrode and then sintered at 500℃ for 2 hours. In the case of the UC photoanode, transparent TiO2 colloids were screen printed on the FTO and sintered at 500 for 2hours. Reflective TiO2colloids mixed with 5 wt% Y2O3:Er3+/Yb3+nanoparticles were subsequently screen-printed on-top of the TiO2film and sintered at 500℃ for 2 hours. The photoanodes were placed on a dielectric barrier discharge (DBD) grounded plate electrode of DBD, then the TiO2film was treated using DBD under room air conditions for 10 minutes. The distance between the surface of the photoelectrode and the DBD electrodes was 5 mm. After the DBD treatment, the photoanodes were finally soaked in the dye (Solaronix N-719 0.2mM/L in ethanol) solution for 24 hours. Eventually the sandwich-type DSSC were fabricated with platinum-coated FTO glass and iodine electrolyte. 2.2 DBD plasma treatments Plasma treatments of upconverting nanoparticle films were carried out using a scalable dielectric barrier discharge device [3]. The device consisted of 20 electrodes of a stainless rod of 1 mm outer diameter and 60 mm length covered with a ceramic tube of 2 mm outer diameter. The electrodes were arranged parallel to each other at a gap of 0.2 mm. The discharge voltage and frequency were 7.96 kV and 9.2 kHz, respectively. The discharge power, which was obtained from Q-V Lissajous characteristics, was 2.17 W. 3. Results and Discussion The photoluminescence spectra of upconversion (UC) nanoparticles under IR laser diode excitation (λ= 980 nm) for three different laser power were measured. We also confirmed both green and red UC emissions, corresponding to the Yb (5F5/2-2Fj) and Er (4F7/2-4Ij) transitions. This indicates that the up converters we developed are capable of transforming NIR radiation into visible light thereby contributing to more photogeneration and have the potential for enhancement of photovoltaic performance of DSSCs. The device characteristics (short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), of the corresponding DSSC devices are showed in Figure 1. The DSSC with the DBD treated TiO2/Y2O3:Er3+/Yb3+composite double layer had a Jscvalue of 10.08 mA. Also, the voltage of the DSSC increased from 0.70 to 0.72 V. The overall efficiency of the DSSC increased from 4.31 % for the untreated TiO2/Y2O3:Er3+/Yb3+composite double layer to 5.15 % for the treated composite double layer. The conceivable reasons for the improvement of the plasma DBD treated cells are as follows [4]; a)Plasma treatment causes surface modification on the TiO2/Y2O3:Er3+/Yb3+double composite film, which enhances the light absorption by the film particles (not by the adsorbed dye). b) Plasma treatment increases the specific surface area of the composite film by changing the surface morphology of the film particles. This increases the amount of the dye adsorbed by the composite film. 4.

Effect of seed layer on the performance of ZnO nanorods-based photoanodes for dye-sensitized solar cells

In this paper, zinc oxide nanorods (ZnO NRs) were synthesized by chemical bath deposition (CBD) method at 90 °C by using zinc nitrate hexahydrate and hexamethylenetetramine as precursors. In a first stage, the ZnO NRs were grown on un-seeded and pre-seeded fluorine-doped tin oxide (FTO) glass substrates by direct CBD method to study the effect of the ZnO seed layer on the NRs structural, morphological and optical properties. The X-ray diffraction (XRD) analysis performed on the pre-seeded NRs revealed a pure ZnO hexagonal wurtzite crystalline phase, while the Field Emission Scanning Electron Microscopy (FESEM) unveiled that the pre-seeded NRs exhibit a smaller diameter, higher density, higher aspect ratio and improved orientation along the c-axis with respect to the un-seeded NRs. In a second stage, the powder obtained by aging, centrifuging and drying the precipitates formed during the CBD growth was analyzed by XRD to assess its crystal structure and phase purity and subsequently coated on un-seeded and pre-seeded FTO glass substrates by doctor blade technique. The ZnO NRs-based seeded and non-seeded films fabricated by the two methods were finally used as photoanodes in dye-sensitized solar cells (DSSCs). Interestingly, the employment of pre-seeded ZnO NRs films deposited by doctor blade technique in comparison to the counterpart electrodes synthesized by direct CBD growth has led to a noticeable increase in the DSSC photoconversion efficiency from 0.35 to 1.86%. On the other hand, the inclusion of the seed layer has effectively improved the fill factor of the DSSC I-V curves for both the photoanode deposition techniques.

Advanced Ag/rGO/TiO2 ternary nanocomposite based photoanode approaches to highly-efficient plasmonic dye-sensitized solar cells

This research demonstrates the utilization of newly designed advanced Ag/rGO/TiO2 ternary nanocomposite based photoanode for highly-efficient plasmonic dye-sensitized solar cells (PDSSCs). The Ag/rGO/TiO2 ternary nanocomposite was successfully synthesized by a facile solvothermal approach without deploying any hazardous agent. In order to achieve the higher power conversion efficiency of the PDSSCs, it was necessary to improve the electron injection rate and optical absorbance of the photoanodes. The nanocomposite was characterized by FE-SEM and TEM analyses, which disclosed that the ternary nanocomposite has been synthesized. The incorporation of Ag nanoparticles onto the TiO2 nanoparticles considerably improved the optical parameters because of the localized surface plasmon resonance (LSPR). XRD and EDX spectroscopic techniques were utilized to confirm the synthesis of Ag nanoparticles and rGO. Furthermore, thermal stability of the nanocomposite was investigated by thermal gravimetric analysis (TGA). Ag/rGO/TiO2 ternary nanocomposite based photoanode demonstrated an enhanced power change productivity of 6.87% in PDSSCs, which was 15% higher than that of the pure TiO2 nanoparticles based photoanode. In addition, an enhanced IPCE of 68% was also observed in comparison with the pure TiO2, which was found due to the remarkable conductivity of rGO.

A facile method to produce TiO2 nanorods for high-efficiency dye solar cells

Highly ordered TiO2 nanorods are considered promising for photoanodes in dye-sensitized solar cells due to their high charge transfer rate of photo-generated electrons, but they often suffer from low specific area, which may lead to a low conversion efficiency. Here, we produce long vertical single-crystalline rutile TiO2-nanorod arrays on fluorine-doped tin oxide conductive glass substrates(FTO)by the hydrothermal method. To further increase the specific area, the TiO2-nanorod arrays are etched in a secondary hydrothermal process by hydrochloric acid. The etching time have a major effect on the nanorod microstructure and on the dye-sensitized solar cells efficiency. The best result is reached with 8 h of etching, which results in a record high conversion efficiency of 11.14 ± 0.12% (certified efficiency 10.3%) under full sunlight illumination (AM 1.5 G, 100 mW/cm2). The record cell has an open voltage of 0.79 V and a short current density of 21.59 mA/cm2. The proposed manufacturing approach of TiO2 nanorods is highly potential for producing high-efficiency dye-sensitized solar cells.

Hetero-seed meditated method to synthesize ZnO/TiO2 multipod nanostructures with ultra-high yield for dye-sensitized solar cells

ZnO multipod nanostructures are widely used for their unique structures. However, the large-scale synthesis of these materials is a challenge for the practical applications. In this paper, we used a hetero-seed mediated hydrothermal method to synthesize ZnO/TiO2 multipod nanostructures with ultra-high yield. The TiO2 nanoparticles were used as the seeds and nucleated centers for the following ZnO nanorods growth, in which these ZnO nanorods scattered from the TiO2 nanoparticles to form ZnO/TiO2 multipod nanostructures. The diameter and length of these ZnO nanorod branches were controlled by the amount of TiO2 nanoparticles. The yield of pure ZnO/TiO2 multipod nanostructures can reach 20.0 g/L within 20 min heating time. When used as the anodes of dye-sensitized solar cells (DSSCs), a photoelectric conversion efficiency of 3.1% has been achieved when using these ZnO/TiO2 multipod nanostructures as the anodes of DSSC. This is due to the one-dimensional (1D) nanostructures are promising by fastening electron transport to reduce the charge recombination. As a result, this provides a simple method to synthesize ZnO/TiO2 multipod nanocomposites with high yield and low cost, which can be used as the photoanodes for high efficient DSSCs and photocatalysts.

On the assessment of incorporation of CNT-TiO2 core-shell structures into nanoparticle TiO2 photoanodes in dye-sensitized solar cells.

Herein, we report dye-sensitized solar cells (DSCs) based on conventional nanocrystalline TiO2 photoanodes decorated with one-dimensional (1D) CNT-TiO2 core-shell structures (CTH). The core-shell nanotubes are synthesized by a simple sol-gel template-assisted method via in situ deposition of TiO2 on the surface of non-covalently functionalized CNTs. The core-shell nanotubes are well characterized by various techniques. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images show that formation of the TiO2 shell on the surface of the CNT core follows a layer or Frank-van der Merwe growth mode, resulting in a highly uniform interface with excellent charge transfer from the TiO2 conduction band into the CNTs. The thickness and crystal structure of the TiO2 shell can be tailored by controlling the processing parameters. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy verify that CNTs have no surface defects and are well preserved using the employed method and the subsequent heat treatment in air, respectively. UV-vis spectroscopy and photoluminescence spectroscopy reveal an extension to visible regions with an increase in overall intensity and a significant reduction in charge recombination due to a shift of the Fermi level toward positive potentials. We find an increase by up to 37% in the DSC device's power conversion efficiency by incorporating the CNT-TiO2 core-shell nanotubes into the nanoparticle TiO2 photoanode due to the charge recombination reduction and electron injection enhancement.