ZnO photoluminescent quantum dots with down-shifting effect applied in solar cells (original) (raw)
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Improvement of the solar cell efficiency by the ZnO nanoparticle layer via the down-shifting effect
Microelectronic Engineering, 2014
External quantum efficiency a b s t r a c t A down-shifting material can generate one low-energy photon for every one incident high-energy photon. When such a material is placed on the front side of a photovoltaic solar cell, it has the potential to enhance the overall efficiency of the PV device by emitting photons in the spectral range where the solar cell efficiency is higher. This paper examines the application of ZnO nanoparticles as a luminescent down-shifting layer (LDSL) on the Si-based, CIGS and CdTe photovoltaic devices. The experimental results measured on a Si-based photovoltaic cell with a top luminescent down-shifting layer are analyzed.
Nanostructured metal oxides are promising candidate for cost efficient solar cells. A key advantage of using metal oxides as electron acceptors is the capability to produce rigid, nanocrystalline structures that present a direct and ordered path for photo-generated electrons to the collecting electrode. This may be done using templated porous structures, tetrapods, or vertically aligned nanorods. In this work, ZnO nanorods were synthesized via a low temperature hydrothermal process on a ZnO thin film coated FTO substrate. CdS quantum dots (QD) were then deposited on ZnO nanorods by chemical bath deposition. Fabricated ZnO nanorods and CdS QD coated ZnO nanorods were characterized using Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-Vis spectroscopy techniques. FESEM micrographs confirm that the nanorods were vertically oriented and well-aligned over the substrate. The length of the ZnO nanorods was determined as 500 nm with diameters ranging from 25 to 50 nm. An XRD diffraction pattern indicates the presence of ZnO and CdS phases adopting the typical hexagonal wurtzite and cubic zinc blende structure, respectively. TEM image shows the average size of fabricated CdS quantum dots was about 5 nm. The strong absorption peak over the near infra-red region ill UV-Vis-NIR spectra also ensured the presence of crystalline CdS on the ZnO nanorods array. Quantum dots sensitized solar cell (QDSSC) was successfully fabricated using CdS QDs and vertically aligned ZnO nanorods. The cell yields a short circuit current density over 1 mACln· 2 and resulting an overall power conversion efficiency over 0.3 % under AM 1.5 irradiation (80 mW/cm 2 ).
CdSe quantum dots sensitized ZnO nanorods for solar cell application
Materials Letters, 2018
Sol gel dip coating method has been used for preparing ZnO nanorods. ZnO nanorods have been sensitized using CdSe quantum dots by simple chemical method. Uniform coverage of quantum dots on ZnO nanorods is observed. The structural, optical and morphology of the ZnO nanorods, CdSe quantum dots and CdSe quantum dot sensitized ZnO nanorods have been studied. The presence of CdSe quantum dots in ZnO nanorods based film is clearly seen in FESEM and TEM image and the elements Zn, O, Cd and Se present in the film was confirmed by EDAX analysis. FTO/CdSe quantum dot-ZnO nanorods/electrolyte/platinum structure based solar cell has been fabricated and the cell efficiency has been found to be 2.1%.
Performance of colloidal CdS sensitized solar cells with ZnO nanorods/nanoparticles
Beilstein Journal of Nanotechnology, 2017
As an alternative photosensitizer in dye-sensitized solar cells, bovine serum albumin (BSA) (a nonhazardous protein) was used in the synthesis of colloidal CdS nanoparticles (NPs). This system has been employed to replace the commonly used N719 dye molecule. Various nanostructured forms of ZnO, namely, nanorod and nanoparticle-based photoanodes, have been sensitized with colloidal CdS NPs to evaluate their effective performance towards quantum dot sensitized solar cells (QDSSCs). A polysulphide (S x 2−)-based electrolyte and Cu x S counter electrode were used for cell fabrication and testing. An interesting improvement in the performance of the device by imposing nanorods as a scattering layer on a particle layer has been observed. As a consequence, a maximum conversion efficiency of 1.06% with an open-circuit voltage (V OC) of 0.67 V was achieved for the ZnO nanorod/nanoparticle assembled structure. The introduction of ZnO nanorods over the nanoparticle led to a significant enhance...
Advanced Functional Materials, 2008
ZnO films consisting of either polydisperse or monodisperse aggregates of nanocrystallites were fabricated and studied as dye-sensitized solar-cell electrodes. The results revealed that the overall energy-conversion efficiency of the cells could be significantly affected by either the average size or the size distribution of the ZnO aggregates. The highest overall energy-conversion efficiency of $4.4% was achieved with the film formed by polydisperse ZnO aggregates with a broad size distribution from 120 to 360 nm in diameter. Light scattering by the submicrometer-sized ZnO aggregates was employed to explain the improved solar-cell performance through extending the distance travelled by light so as to increase the lightharvesting efficiency of photoelectrode film. The broad distribution of aggregate size provides the ZnO films with both better packing and an enhanced ability to scatter the incident light, and thus promotes the solar-cell performance.
ZnO nanoparticles were synthesized via novel Sol-gel route. The effects of pH variation as well as ageing were studied. The nanoparticles were synthesized with two different pH levels viz. pH 7 and pH 10. It was found that the size of the nanoparticles increased from 19 to 39.6 nm with increase in pH level from 7 to 10. Further the effect of ageing on the ZnO nanoparticles was studied. It was found that the crystallite size as well as the crystallinity of the nanoparticles increased with ageing. The crystallite size increased from 19 to 32.8 nm for pH 7 and from 39.6 to 42 nm for pH 10 with ageing. The intensity of the XRD peaks increased drastically with ageing primarily due to increase in crystallite size of nanoparticles. The nanoparticles were further characterized using TEM. The particle size obtained by TEM was same as crystallite size obtained by XRD. The synthesized ZnO nanoparticles can be used as a suitable material for application in quantum dot sensitized solar cells (QDSSCs).
Vacuum-Evaporated ZnO Photoanode, Applied in Quantum Dot-Sensitized Solar Cells (CdS-CdSe)
physica status solidi (a), 2018
In this research, the application of vacuum-evaporated nanostructured ZnO thin films as a photoanode and its use in quantum dot-sensitized solar cells (QDSSCs) is reported. Quantum dots (CdS/CdSe) are deposited through successive ionic layer adsorption and reaction (SILAR) technique. Thirty nanometers average size ZnO nanoparticles synthesized from solution are used as a source, resultant thickness starts from 200 nm to 3 microns. Average size and crystal phase identification are done by XRD. Scanning electron microscopy (SEM), UV-Vis, profilometer, and J-V are used to determine morphology, elemental composition, transmittance, band gap, thickness, and efficiency of the solar cell, respectively. Characterization of efficiency is carried out on different film thicknesses. A total efficiency of 1.25% is obtained for a specific film thickness under 1.5 AM.
Low-Temperature ZnO Thin Film and Its Application in PbS Quantum Dot Solar Cells
VNU Journal of Science: Natural Sciences and Technology
Zinc oxide (ZnO) has been widely deployed as electron conducting layer in emerging photovoltaics including quantum dot, perovskite and organic solar cells. Reducing the curing temperature of ZnO layer to below 200 oC is an essential requirement to reduce the cell fabrication cost enabled by large-scale processes such as ink-jet printing, spin coating or roll-roll printing. Herein, we present a novel water-based ZnO precursor stabilized with labile NH3, which allow us to spin coat crystalline ZnO thin films with temperatures below 200 oC. Thin film transistors (TFTs) and diode-type quantum dot solar cells (QD SCs) were fabricated using ZnO as electron conduction layer. In the QD SCs, a p-type 1,2-ethylenedithiol treated PbS QDs with a bandgap of 1.4 eV was spin-coated on top of ZnO layer by a layer-by-layer solid state ligand exchange process. Electron mobility of ZnO was about 0.1 cm2V-1s-1 as determined from TFT measurements. Power conversion efficiency of solar cells: FTO/ZnO/PbS...