Self-assembled ultra small ZnO nanocrystals for dye-sensitized solar cell application (original) (raw)
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Nanoscale research letters, 2014
Mesoporous ZnO nanoparticles have been synthesized with tremendous increase in specific surface area of up to 578 m 2 /g which was 5.54 m 2 /g in previous reports (J. Phys. Chem. C 113:14676-14680, 2009). Different mesoporous ZnO nanoparticles with average pore sizes ranging from 7.22 to 13.43 nm and specific surface area ranging from 50.41 to 578 m 2 /g were prepared through the sol-gel method via a simple evaporation-induced self-assembly process. The hydrolysis rate of zinc acetate was varied using different concentrations of sodium hydroxide. Morphology, crystallinity, porosity, and J-V characteristics of the materials have been studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), BET nitrogen adsorption/desorption, and Keithley instruments.
Nanoporous ZnO Photoelectrode for Dye-Sensitized Solar Cell
Journal of Nanomaterials, 2012
Nanoporous and macroporous structures were prepared by using self-assembled monolayer (SAM) onto ZnO thin films in order to investigate the efficiency of dye-sensitized solar cells (DSSCs) produced using these films. Using SAM on ZnO thin films, it is obtained successfully assembled large-area, highly ordered porous ZnO thin films. Varying nanoporous radius is observed between 20 and 50 nm sizes, while it is 500ā800 nm for macroporous radius. The solar conversion efficiency of 2.75% and IPCE of 29% was obtained using ZnO nanoporous/N719 dye/Iā/I3-electrolyte, while macroporous ZnO given solar conversion efficiency of 2.22% and IPCE of 18%.
Hierarchically Assembled ZnO Nanocrystallites for High-Efficiency Dye-Sensitized Solar Cells
Angewandte Chemie International Edition, 2011
Photoelectrochemical cells are promising devices for cheap, environmentally compatible, and large-scale solar energy conversion as an alternative to conventional solid-state semiconductor solar cells. Among excitonic cells, dyesensitized cells (DSCs) exhibit the highest performance in terms of energy conversion efficiency and long term stability, despite the fact that the efficiency remains below 13 % because of the intrinsic limitation in charge transport. The structure of the photoelectrodes is crucial in determining the functional properties of the photoelectrochemical system. In particular, the photoanode consists of a mesoporous wideband-gap oxide semiconductor film with a high specific surface (typically a thousand times larger than the bulk counterpart). To date, the highest photoconversion efficiency (PCE) has been achieved with film consisting of 20 nm TiO 2 nanocrystallites sensitized by different dye molecules (11.1 % for N719 dye, over 10 % for "black dye", and 11.4 % for C101, ). In addition to TiO 2 , a series of other ntype metal oxide semiconductors can in principle be used in DSCs, such as ZnO, SnO 2 , and In 2 O 3 . Much attention has been recently devoted to ZnO owing to its higher electron mobility and similar electronic band structure with respect to TiO 2 . Various strategies have been addressed to enhance PCE in ZnO-based DSCs, which are mainly based on tailoring the geometrical and structural features of ZnO. A possible solution to reduce electron recombination could be the use of one-dimensional nanostructures that are able to provide a direct pathway for the rapid collection of photogenerated electrons. However, only low PCE has been achieved to date, mainly because of the reduced internal surface area of the nanostructures. Hybrid structures have also been tested to improve light collection, such as combination of nanoparticles and nanowires (maximum PCE = 4.2 %), or hierarchical nanowires (maximum PCE = 2.63 %). Another strategy to enhance PCE is application of hierarchical photoanodes composed of large aggregates of nanocrystallites, which can act as light scattering centers while maintaining a high specific surface area. The synthetic procedure of photoanode preparation is crucial to improve PCE: an optimized photoanode composed of just ZnO nanoparticles without any geometrical feature for light confinement or enhanced electron transport resulted in the highest value of PCE (6.58 %) for a ZnO-based DSC. Herein we present the fabrication and characterization of hierarchically structured ZnO-based photoanodes in DSCs to enhance the PCE. Our approach addresses specifically the following points: 1) High optical density of the sensitized layer, allowing complete light absorption in the spectral range of the dye; 2) high light scattering of the absorbing layer, enhancing the time spent by light inside the sensitized film and improving light absorption; and 3) inhibition of back electron transfer between the conducting layer at the anode and the electrolyte. The films are prepared by the simple, cheap, and large-area-scalable spray pyrolysis method. The films are composed of polydispersed ZnO aggregates consisting of nanosized crystallites while submicrometer-sized aggregates act as efficient light scattering centers and nanoparticles provide the mesoporous structure and the large specific surface area needed for high dye loading. Additionally, a ZnO compact layer is intentionally formed between the conducting substrate and the layer composed of polydispersed aggregates. Such a layer acts as an efficient blocking layer for electron back reaction between the conducting glass at the anode and the electrolyte, improving the functional properties of the cells. This is the main innovation with respect to the work of Cao and co-workers, leading to unprecedented PCE up to 7.5 %, which is larger than ZnO nanoparticles (6.58 %), hierarchically structured ZnO without a blocking layer (5.4 %), and hierarchically arranged ZnO nanowires (2.63 %). As a further benefit, our method is extremely fast (no more than 1.5 h for the complete processing of a photoanode, while typically 8 h or 10 to 14 h are required), enabling its technological implementation.
Solid-state dye-sensitized solar cells based on ZnO nanocrystals
Nanotechnology, 2010
We report on the development of solution-processed ZnO-based dye-sensitized solar cells. We fabricate mesoporous ZnO electrodes from sol-gel processed nanoparticles, which are subsequently sensitized with conventional ruthenium complexes and infiltrated with the solid-state hole transporter medium 2, 2', 7, 7'-tetrakis-(N, N-di-p-methoxyphenylamine)-9, 9'-spirobifluorene (spiro-OMeTAD). Starting from ZnO nanorods synthesized from solution, we investigate the porous ZnO film morphology using various precursor
Self-Assembled ZnO Nanosheet-Based Spherical Structure as Photoanode in Dye-Sensitized Solar Cells
Journal of Electronic Materials, 2017
High surface area and enhanced light scattering of ZnO nanosheet aggregates have made them a promising active layer candidate material for fabrication of nanostructure dye-sensitized solar cells. Here, we propose a facile preparation method of such ZnO nanosheet structures, and in order to verify their applicability as photoanode material for dye-sensitized solar cells, we employ morphological, optical, structural and electrical measurements. The results reveal the high surface area available for dye molecules for enhancing adsorption, high light scattering and competitive power conversion efficiencies compared to the works in literature. Finally, the device is optimized with respect to the photoanode thickness. The favorable features shown here can extend the application of the structure to other types of sensitization-based perovskite and quantum dot solar cells.
ZnO Nanostructures for Dye-Sensitized Solar Cells
Advanced Materials, 2009
This Review focuses on recent developments in the use of ZnO nanostructures for dye-sensitized solar cell (DSC) applications. It is shown that carefully designed and fabricated nanostructured ZnO films are advantageous for use as a DSC photoelectrode as they offer larger surface areas than bulk film material, direct electron pathways, or effective light-scattering centers, and, when combined with TiO 2 , produce a core-shell structure that reduces the combination rate. The limitations of ZnO-based DSCs are also discussed and several possible methods are proposed so as to expand the knowledge of ZnO to TiO 2 , motivating further improvement in the power-conversion efficiency of DSCs.
Zinc oxide nanostructure-based dye-sensitized solar cells
Journal of Materials Science, 2017
Developing new technologies that could lead to alternatives to the traditional silicon-based solar panels, and to efficiently light the world in the future, is critically important because of limited natural petroleum resources. Dye-sensitized solar cells (DSSCs) are promisingly efficient and clean hybrid, organicinorganic, low-cost molecular solar cell devices. The key components of DSSCs are the organic dyes that play the role of a photosensitizer-like the chlorophyll of a green plant that is responsible for photosynthesis-and nanostructured semiconductor metal oxides. Because of their unique, multifunctional properties, zinc oxide (ZnO) nanostructures are promising materials to use to create photoanodes for DSSCs. This review looks at recent developments in the field of ZnO-based DSSC devices; synthesis of ZnO nanostructures with variable morphologies, including nanorods, nanofibers, nanotubes, nano-/microflowers, thin sheets, and nanoaggregates; factors that control the growth and morphologies of these nanomaterials; and the role of crystallographic planes for the synthesis of versatile ZnO nanostructures. This review also covers photoelectrode fabrication, DSSC device components, nature and chemical features of the dyes used as photosensitizers, and operational principles. In addition, various photovoltaic parameters such as current density, open-circuit voltage, fill factor, photoconversion efficiency, and factors that influence these parameters for ZnO-based DSSCs are summarized and discussed.
Solution-derived ZnO nanostructures for photoanodes of dye-sensitized solar cells
Energy & Environmental Science, 2011
Solution-phase derived ZnO nanostructures have triggered considerable interest and become the mainstream route to obtain low-cost and large-scale electrode materials for dye-sensitized solar cells (DSSCs). The article reviews recent progress in liquid-phase synthesis methods for preparing ZnO nanostructures as the photoanodes of the DSSCs. A few classic paradigms and new advancements in the ZnO nanostructures made by our group are demonstrated. The effects of ZnO nanostructured films with different morphologies, prepared by solution-phase approaches, on the performance of DSSCs are discussed. Finally, various liquid-phase methods of ZnO nanostructure synthesis are summarized and compared to allow further exploration of the ways to improve the photoelectric conversion efficiency of DSSCs.
Electrochimica Acta, 2008
In this work, the morphology of ZnO materials could be controlled by changing the capping agent at constant alkali solution in hydrothermal process. ZnO nanomaterials with the structure of flowers, sheet-spheres and plates were obtained with the capping agent of ammonia, citric acid and oxalic acid, respectively. Thus prepared ZnO nanomaterials were characterized and applied as the photo-anode materials for dye-sensitized solar cell. All synthesized ZnO nanomaterials possessed high crystalline wurtzite structures grown in the (0 0 1) direction with the size of 2-4 m, which consist of ZnO units around 20-400 nm. Among them, Sheet-sphere ZnO showed the highest crystallinity, surface area and uniform film morphology, resulting in the significantly improved PV performance with the overall conversion efficiency of 2.61% in dye-sensitized solar cell (DSSC) fabricated with sheet-sphere ZnO. It is notable that the ZnO materials with sphere structure may be the optimal photo-anode material among various ZnO nanomaterials for DSSC.
2018
ZnO nanoparticles (ZnO NPs) were synthesized using hydrothermal and sol-gel techniques using zinc acetate dihydrate (Zn (CH3COO)2.2H2O) as a row material and methanol as a solvent. The structural properties of ZnO NPs were studied using EDX, XRD, TEM, and the optical properties were characterized using UV-VIS and PL spectroscopies. The synthesized ZnO NPs showed high purity and revealed a wurtzite (hexagonal) crystal structure with particle size (D) ranged from 25 nm to 28 nm. The UV-VIS absorption spectra of ZnO NPs samples and sensitizing dyes were performed. The obtained ZnO NPs exhibited the direct optical bandgap 3.15 eV. Dye-sensitized solar cells (DSSCs) were fabricated using synthesized ZnO NPs as a semiconducting layer, which was dyed with different low cost dyes such as Eosin B (EB), Eosin Y (EY) and Rhodamine B (RB) that was used to sensitize the photoanode (ZnO NPs). The experimental results showed a significant efficiency for the fabricated DSSCs of synthesized ZnO NPs ...