Influence of defect density on the ZnO nanostructures of dye-sensitized solar cells

Abstract

The relationship between bilayer nanostructure, defect density and dye-sensitized solar cell (DSCC) performances was investigated. By adjusting bilayer nanostructures, defect density of ZnO nanodendrite-nanorods structure was decreased comparing to that of nanoflowernanorods structure. The performances of DSCC based on ZnO nanodendrites-nanorods structure and nanoflowernanorods structure were studied by Raman spectrum, room temperature photoluminescence, dye loading, photocurrent density-voltage characteristic and open-circuit voltage decay (OCVD) technique. The device with nanodendritenanorods structure has lower charge recombination rate and prolonged electron lifetime due to its microstructure feature.

Defects in Chemically Synthesized and Thermally Processed ZnO Nanorods: Implications for Active Layer Properties in Dye-Sensitized Solar Cells

“…Although the synthesis and DSSC performance of various solution-derived ZnO rods have been reported in a series of reviews and articles, the efficiencies of most of them were below 1% with a few exhibiting above 1% efficiency. − In this respect, our data are far superior in that we were able to prepare ZnO rods by a very simple solution technique without the use of any surfactant or structure-directing agent exhibiting much enhanced DSSC efficiency as compared to many of the reported values on solution processed ZnO rods. − ,− …”

“…This sample exhibited a higher open circuit voltage ( V oc ) of 0.71 V and a lower fill factor (FF) of 35.2. The lower free carrier density in the 300 °C annealed sample could induce a positive shift of the Fermi level of ZnO rods that could further reduce the gap between the I – /I 3– redox couple and Fermi level, thereby minimizing the V oc followed by an improvement in fill factor, which is less recombination and thereby enhances the efficiency indirectly. ,,, The as-prepared and 300 °C annealed ZnO rods having less oxygen vacancy density exhibited relatively less V oc of 0.66 and 0.67 V, respectively (Figure a) and a higher fill factor of 43.58% and 45.29%, respectively (Figure c). The photoluminescence and Raman spectroscopic studies confirmed that the 300 °C annealed rods have minimum defects with improved crystal quality.…”

“…Among the few reports available on the defect related DSSC performance, the paper by Hsu et al, on the performance of ZnO rods prepared by hydrothermal and vapor deposition techniques, is noteworthy . Wong et al, on the other hand, investigated the influence of optical properties of ZnO particles on the DSSC performance, whereas Lou et al reported the influence of defect density on ZnO rods and Makhal et al reported the role of resonance energy light based on defect emission in ZnO. − Therefore, our basic objective was to investigate and correlate the influence of native defects on the solution processed ZnO rods and their thermally annealed counterparts and their performance as photo anodes in DSSC. Here, we have prepared ZnO rods by a sonication-induced precipitation methodology followed by simple heating in an aqueous media at 80 ± 5 °C for 6 h. We have investigated in detail the properties of the prepared ZnO rods and have revealed an interesting correlation between the structural defects, photoluminescence properties, and solar cell performances of DSSC fabricated using the as-prepared and thermally annealed ZnO rods.…”

Femtosecond Luminescence Imaging for Single Nanoparticle Characterization

“…The vast majority of studies conducted on point defects have focused on either identifying or computationally predicting their stability. , Other works describe changes in defect density qualitatively through the increase or decrease of a spectroscopic band signal . For quantifying defect density, techniques such as deep level transient spectroscopy (DLTS) and impedance spectroscopy are the most commonly used but both require contacts for an external electrical connection and DLTS is also only sensitive to deep level defects. , Techniques that do not require contacts are usually either spectroscopy or microscopy based such as lyoluminescence and Raman spectroscopy. , These methods are, however, often restricted to bulk sample measurements.…”

Synthesis of Binary Bi2S3/ZnO Nanorod Array Heterostructure and Their Photoelectrochemical Performance

“…To achieve this aim, metal oxide semiconductors are utilized as a photoanode in the photoelectrochemical cells. Among oxide-based semiconductors, ZnO is the most encouraging candidate due to its high earth plenty, nontoxicity, and unique physical and chemical properties for many photovoltaic applications [1]. Owing to the large band gap energy of ZnO (3.37 eV), the electron-hole (e --h + ) pairs are formed when it is irradiated by ultraviolet (UV) light which represents merely (4%) of the entire solar light spectrum.…”