Layer In Dye-sensitized Solar Cells Research Articles

Photovoltaics literature survey (no. 149)

Photovoltaics literature survey (no. 149)

Blocking the Charge Recombination with Diiodide Radicals by TiO2 Compact Layer in Dye-Sensitized Solar Cells

The addition of a compact titanium dioxide (TiO2) layer between the fluorine-doped tin oxide (FTO) coated glass substrate and the mesoporous TiO2 layer in the dye-sensitized solar cell (DSC) based on the iodide/triiodide redox couple (I−/I3−) is known to improve its current-voltage characteristics. The compact layer decreases the recombination of electrons extracted through the FTO layer with I3− around the maximum power point. Furthermore, the short-circuit photocurrent was improved, which previously has been attributed to the improved light transmittance and/or better contact between TiO2 and FTO. Here, we demonstrate that the compact TiO2 layer has another beneficial effect: it blocks the reaction between charge carriers in the FTO and photogenerated diiodide radical species (I2−•). Using photomodulated voltammetry, it is demonstrated that the cathodic photocurrent found at bare FTO electrodes is blocked by the addition of a compact TiO2 layer, while the anodic photocurrent due to reaction with I2−• is maintained.

Performance of CoTiO3 as an oxide perovskite material for the light scattering layer of dye-sensitized solar cells

CoTiO3 particles with mirror-like facets were employed as the mono- and bi-layered scattering films into nanoparticle TiO2 DSSCs.

One-step synthesis of hierarchical SnO2/TiO2 composite hollow microspheres as an efficient scattering layer for dye-sensitized solar cells

Hierarchical SnO2/TiO2 composite hollow microspheres were synthesized via one-step hydrothermal route by using titanium tetrabutoxide as titanium source and potassium stannate and tripolycyanamide as co-additive, and the samples were characterized by XRD, BET, SEM and TEM measurements. The results denoted that the synthesized microspheres with a diameter of ca 500–1000 nm were assembled by thin nanosheets and possessed a large surface area of 199.3 m2 g−1. In addition, EDX and element mapping measurements indicated that a small amount of SnO2 nanoparticles uniformly distributed among the nanosheets of microspheres. The hierarchical microspheres simultaneously facilitated dye adsorption, light harvesting, and electron transport, giving rise to a high photovoltaic conversion efficiency of 8.70% when applied as scattering layer for dye-sensitized solar cells, which was a 28.1% improvement compared to that of bare nanocrystalline TiO2 (6.79%, Dyesol) based cell.

Microwave-assisted solvothermal synthesis of worms-like TiO2 nanostructures in submicron regime as light scattering layers for dye-sensitized solar cells

Addition of light scattering layer over the active layer is adopted as a strategy to improve the light harvesting ability and thereby the interaction of light with the anchored dye molecules could be enhanced. Worms-like TiO2 nanostructures were synthesized by microwave assisted solvothermal synthesis by simple chemical modification method using urea. Characteristic anatase TiO2 peaks were confirmed using X-ray diffraction analysis. Optical properties were studied using UV–visible diffuse reflectance and photoluminescence spectroscopy. Optical studies of the prepared material revealed characteristic wide bandgap semiconductor properties. FESEM and TEM images confirmed the presence of nanostructures in the prepared samples. The mesoporous nature of the prepared TiO2 nanostructures was confirmed using BET isotherm. Chemical composition and the respective oxidation states of TiO2 were studied using X-ray photoelectron spectroscopy. The prepared TiO2 nanostructures were coated as a light scattering layer over the active layer of the photoanode and its performance was studied.

Characteristics of GZO/IZO Dual-Layer as an Electron Transport Layer in Dye-Sensitized Solar Cell

Characteristics of GZO/IZO Dual-Layer as an Electron Transport Layer in Dye-Sensitized Solar Cell

Solvothermal Synthesis of Ferroelectric BaTiO3 Nanoparticles and Their Application to Dye-sensitized Solar Cells

Cubic BaTiO3 (C-BT) and tetragonal BaTiO3 (T1-BT) nanoparticles were prepared by a solvothermal method with controlling the Ba/Ti precursor ratio. Triethanolamine was additionally employed in the synthesis to obtain ferroelectric BaTiO3 with improved particle size distribution and tetragonality (T2-BT). The prepared nanoparticles were thoroughly characterized by scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, photoluminescence, and second-harmonic generation. Importantly, the BaTiO3 nanoparticles were introduced into the scattering layer of dye-sensitized solar cells and T2-BT showed better power conversion efficiency than C-BT and T1-BT.

Blue TiO2 polymorph: An efficient material for dye-sensitized solar cells fabricated using a low-temperature sintering process

Recently, surface-disordered or non-stoichiometric TiO2, such as blue TiO2 (B-TiO2), has received much attention owing to its unique properties, such as structural disorder near the surface and the existence of Ti3+ ions and oxygen vacancies. Therefore, surface-disordered TiO2 has been applied for microwave absorption, photocatalysis, in photoelectrochemical sensors and rechargeable lithium-ion batteries. In this work B-TiO2, a polymorph consisting of nanoparticles, nanotubes and nanosheets, was successfully synthesized and employed as a semiconductor layer in dye-sensitized solar cells (DSSCs) fabricated using a low-temperature heat treatment process (120 °C). Based on the analyses of the experimental results regarding the structure and those from the characterization of B-TiO2, and its application to DSSCs, it has been found that the B-TiO2 material has an effect on electron-hole pair separation. The conversion efficiency of the B-TiO2 DSSC (BTiO2-DSSC) was 6.18%, whereas that of the TiO2-P25 DSSC (P25-DSSC) was 3.61%, and that of the TiO2 polymorph DSSC (PTiO2-DSSC) which is the precursor of B-TiO2 was 4.51%.

Assessment of Photoelectrode Material Based on (TiO2)<sub>1-x</sub> / (Al<sub>65</sub>Cu<sub>24</sub>Fe<sub>11</sub>)<sub>x</sub> in Dye-Sensitized Solar Cell Applications

This paper presents the results obtained for incorporating the Al65Cu24Fe11material with the conventional TiO2 as the electron injection layer in dye-sensitized solar cells. The icosahedral phase of the Al-Cu-Fe system has attractive physical and optical properties at the target composition, and is obtained by synthesizing the material via the facile high energy ball milling process to ensures the highest possible interdiffusion of elemental powders, followed by heat treatment. The evolution of the i-phase is confirmed via X-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The optical absorption and electrical properties of the compound are investigated by spectrometry, four probe measurement and Mott-Schottky analysis, respectively. Different cells with different percentages (x value) of (TiO2)1-x/(Al65Cu24Fe11)xare constructed and tested to obtain the electrical characteristic curves, efficiency and fill factor to quantify the effect of the proposed material mixture.

Low Cost Fabrication of Si NWs/CuI Heterostructures.

In this paper, we present the realization by a low cost approach compatible with silicon technology of new nanostructures, characterized by the presence of different materials, such as copper iodide (CuI) and silicon nanowires (Si NWs). Silicon is the principal material of the microelectronics field for its low cost, easy manufacturing and market stability. In particular, Si NWs emerged in the literature as the key materials for modern nanodevices. Copper iodide is a direct wide bandgap p-type semiconductor used for several applications as a transparent hole conducting layers for dye-sensitized solar cells, light emitting diodes and for environmental purification. We demonstrated the preparation of a solid system in which Si NWs are embedded in CuI material and the structural, electrical and optical characterization is presented. These new combined Si NWs/CuI systems have strong potentiality to obtain new nanostructures characterized by different doping, that is strategic for the possibility to realize p-n junction device. Moreover, the combination of these different materials opens the route to obtain multifunction devices characterized by promising absorption, light emission, and electrical conduction.

Non-ohmic resistance effects of the AZO and TiZO as a blocking layer in dye-sensitized solar cells (DSSCs)

Presented in this paper is the result of a study on the utilization of Al-doped ZnO (AZO) and Ti-doped ZnO (TiZO) as a blocking layer (BL) in Dye-Sensitized Solar Cells (DSSCs). The DSSCs structure was FTO/BL/TiO2/dye/electrolyte/Pt on FTO. The crystallinity and crystallite size of those BLs were shown to be affected by the dopant type and its concentration. From the photovoltaic characteristics of those DSSCs, the TiZO layer showed better contribution in enhancing the open voltage as a BL in comparison to the AZO. The effect of these layers on the solar cell characteristics in the fabricated DSSCs was found to be not merely due to the difference in their Ohmic resistance. There is also the contribution of back recombination kinetics from the photoexcited electrons via the dopant states in the AZO and TiZO layers, which are different among the layers due to the difference in dopant states distributions below their conduction bands.

A comparative study between titania and zirconia as material for scattering layer in dye-sensitized solar cells

The photoanode of dye-sensitized solar cells (DSSC) is typically composed of nanocrystalline titania (TiO2) layer that has been sensitized with light-absorbing dye molecules. Large portion of the light, however, could not be efficiently absorbed due to some physical reasons, such as TiO2 crystal size (typically 10-25 nm) that makes the photoanode remains partially transparent to the visible region in the solar spectrum. One of the ways to improve the light harvesting efficiency in DSSC could be achieved by employing an additional scattering layer over the TiO2 electron transport material. In this contribution, we evaluate the effect of light scattering properties on the performance of DSSC. Specifically, the light scattering properties provided from two different scattering materials, i.e. additional TiO2 scattering layer and zirconia (ZrO2) scattering layer, were compared. Both layers were deposited using screen printing technique under the same condition on top of 8 µm thick TiO2 photoanode layer. All samples subsequently received the same thermal annealing treatment at 500 °C and sensitized with ruthenium-based synthetic dyes. Our results revealed that the thickness of the scattering layer for both TiO2 and ZrO2 had a significant effect on the solar cell performance. The best photoconversion efficiency was achieved by samples that were coated with one screen-printing cycle, giving an overall efficiency of 3.50 % and 4.02% for TiO2 and ZrO2, respectively.

The synthesis and application of TiO2 microspheres as scattering layer in dye-sensitized solar cells

Mesoporous TiO2 microspheres have been synthesized via a simple one-plot hydrothermal method and were used as the light scattering layer on top of the P25 TiO2 compact layer to form a double-layer film based photoanode for the dye-sensitized solar cell (DSSC). Characteristics and light scattering properties were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, nitrogen sorption analysis and ultraviolet–visible spectroscopy. Photovoltaic performance of the fabricated DSSC was also investigated. It showed that photoelectric conversion efficiency of the double-layer film based DSSC was increased to 5.61% compared with single P25 compact layer film based (2.67%) and single TiO2 microspheres layer film based (2.14%) DSSC. Improvement of DSSC performance can be attributed to excellent light scattering capability given by mesoporous TiO2 microspheres. Electrochemical impedance spectra analysis also proved that double-layered structure can result in prolonged exciton lifetime, improved charge collection efficiency and decreased charge recombination.

Efficiency enhancement of DSSC by alternating TiO2 active layer

A novel alternating TiO2 structure was used as an active layer for dye-sensitized solar cells. The TiO2 film was prepared with pure TiO2 nanoparticle paste and mixed polystyrene–TiO2 paste to form an alternating configuration of dense TiO2 and micro-/nano-composite porous TiO2. The solar cell efficiency was enhanced from 4.91% to 5.58%. A dense TiO2 layer forms a closer contact with the conducting substrate, and the micro-/nano-composite porous TiO2 layer favorites dye absorption. Thus, their combination offered better performance. This improvement was attributed to the enhancement of light harvesting, more efficient dye absorption, lower resistance, and longer electron lifetime.

Ag@Nb2O5 plasmonic blocking layer for higher efficiency dye-sensitized solar cells.

Engineering photons on a nanoscale via guidance and localization by metal nanostructures has a profound influence on the performance of devices that try to mimic the process of photosynthesis. The conventional route for the synthesis of plasmonic nanoparticles and their integration into the porous structure of the photoanode either directly or after being capped with a dielectric material not only adds to the complexity but also to the cost of the cell. The present study introduces the concept of a plasmonic blocking layer that concurrently acts as a light harvester and an electron-blocking layer in a dye-sensitized solar cell (DSSC), wherein the plasmonic silver nanoparticles are incorporated into an Nb2O5 blocking layer by a simple one-step process. The cell with the plasmonic blocking layer achieves an efficiency of 9.24% when compared with a cell with a non-plasmonic blocking layer (7.6%), registering an impressive enhancement in the efficiency by 22%. Moreover, the cell with the plasmonic blocking layer shows an improvement in the efficiency by 49% when compared with the cell without a blocking layer (6.19%).

Double-shell SnO2/CeO2:Yb,Er hollow nanospheres as an assistant layer that suppresses charge recombination in dye-sensitized solar cells

When SnO2/CeO2:Yb,Er HNSs act as an assistant layer in dye-sensitized solar cells, the photoelectric conversion efficiency is enhanced to 8.66%.

Strategy to improve photovoltaic performance of DSSC sensitized by using novel nanostructured La dopped TiO2-graphene electrodes

A novel series of La/TiO2-graphene (GLT) materials were synthesized, and then used in the production of counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). The electrode properties of various CEs were comprehensively analyzed using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction. DSSCs, based on various CEs, were characterized using electrochemical impedance spectroscopy measurements. DSSCs fabricated using the La/TiO2-graphene nanocomposite CEs yielded an efficiency of 6.75%. The La/TiO2-graphene CEs exhibited efficient electrocatalytic capability, because catalytic La particles were uniformly distributed on the surface of graphene. Moreover, we also demonstrated the effect of a thin compact layer in DSSCs by their architecture with various amounts of graphene materials. The results indicated that a DSSC with a La/TiO2-graphene CE can exhibit an efficiency comparable to that of a platinum (Pt) CE DSSC, and can therefore replace conventional Pt CE DSSCs, to lower the cost of solar cells.

Au/TiO2 Hollow Spheres with Synergistic Effect of Plasmonic Enhancement and Light Scattering for Improved Dye-Sensitized Solar Cells.

Au-decorated TiO2 hollow spheres (Au-THS) have been successfully synthesized via a facile one-pot solvothermal method. The Au-THS hybrid features unique hollow structure with a large specific surface area of 120 m2 g-1 and homogeneous decoration of Au nanoparticles, giving rise to enhanced light harvesting and charge generation/separation efficiency. When incorporated into the active layer of dye-sensitized solar cells (DSSCs), an improved power conversion efficiency of 7.3% is obtained, which is increased by 37.7% compared with the controlled P25 DSSC. The underlying mechanism to rationalize the efficiency enhancement can be mainly attributed to the strong synergistic effect of superior light scattering ability of the THS and the plasmonic-enhanced effect rendered by the Au nanoparticles.

Preparation of plasmonic monolayer with Ag and Au nanoparticles for dye-sensitized solar cells

We fabricated a plasmonic layer by immobilizing both Au and Ag nanoparticles via P4VP on a photoactive layer for dye-sensitized solar cells (DSSCs) to prevent aggregation of metal nanoparticles, to increase absorbance of N719 dye, and to enhance light harvesting and power conversion efficiency (PCE). The optimal conditions for immobilizing these nanoparticles were also examined. With plasmonic Au and Ag nanoparticles, the PCE increased by 8.05% and 5.78%, respectively (plasmonic Au nanoparticles: from 8.82% to 9.53%; plasmonic Ag nanoparticles: from 8.82% to 9.33%). When both Au and Ag nanoparticles were employed in the plasmonic layer, the PCE showed further improvement of 10.17%, corresponding to a 15.31% enhancement. This significant improvement of the PCE could be explained by a broader range of light absorption resulting from the presence of the plasmonic layer.

Double-shell CeO2@TiO2 hollow spheres composites with enhanced light harvesting and electron transfer in dye-sensitized solar cells

A new double-shell hollow structured material with high light harvesting and dye loading level for dye-sensitized solar cells (DSSCs) were synthesized via a one-pot hydrothermal method. When coated with TiO2 shell, a hybrid double-shell CeO2@TiO2 hollow sphere (D-CeO2@TiO2) was performed as scattering layer in dye-sensitized solar cells, which further increase conversion efficiency from 5.27% of bare TiO2 electrode to 7.95%. The enhancement is due to the high dye loading capacity of double shell CeO2 hollow spheres core and high electron transport capacity of TiO2 shell. Our work provides a feasible strategy for preparing multi-shell hollow spheres as scattering layers for high performance solar cells.