Universal photoluminescence evolution of solution-grown ZnO nanorods with annealing: important role of hydrogen donor

Xiao, Huang; Tay, Chuan Beng; Zhan, Zhaoyao; Zhang, C.; Zheng, Lianxi; Venkatesan, T.; Chua, Soo Jin

doi:10.1039/c1ce05882g

Cited by 51 publications

(42 citation statements)

References 42 publications

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“…The intensity of the NBE band varied from 1 for the as-prepared sample to 3.78 for 100°C annealed to 4.91 for 200°C to 5.81 for 300°C to 0.63 for 400°C to 0.57 for 500°C to 0.41 for the 600°C annealed samples. An enhancement of NBE with annealing temperature was reported earlier by Huang et al, for the solution processed ZnO rods, 41,42 and they attributed this to an annealing-induced activation and dissociation of shallow hydrogen donor (H O + ) trapped within the oxygen vacancies. We also noticed such a substantial increase in the NBE on annealing up to 300°C.…”

Section: ■ Experimental Sectionmentioning

confidence: 77%

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

et al. 2014

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We have carried out the effect of post annealing temperatures on the performance of solution-grown ZnO rods as photoanodes in dye-sensitized solar cells. Keeping our basic objective of exploring the effect of native defects on the performance of DSSC, we have synthesized ZnO rods having length in the range of 2-5 μm by a modified sonication-induced precipitation technique. We performed extensive characterization on the samples annealed at various temperatures and confirmed that annealing at 300 °C results in ZnO rods with minimum native defects that have been identified as doubly ionized oxygen vacancies. The electron paramagnetic resonance measurements on the samples, on the other hand, confirmed the presence of shallow donors in the low temperature annealed samples. We also carried out electrochemical impedance measurements to understand the transport properties at different interfaces in the solar cell assembly. We could conclude that solution-processed ZnO rods annealed at 300 °C are better suited for fabricating DSSC with improved efficiency (1.57%), current density (5.11 mA/cm(2)), and fill factor (45.29%). On the basis of our results, we were able to establish a close connection between the defects in the metal oxide electron transporting nano system and the DSSC performance.

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Section: ■ Experimental Sectionmentioning

confidence: 77%

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

et al. 2014

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“…where I ( T ) is the integrated PL intensity at T (K), I 0 is a scaling factor, and P is a process rate parameter [ 19 - 21 ]. It provides important information to the origin of carrier recombination in various semiconductors [ 21 - 23 ]. The dashed line in the inset of Figure 5 is the least square fit of data with Equation 1.…”

Section: Resultsmentioning

confidence: 99%

Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature

et al. 2014

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Vertically aligned ZnO nanorods (NRs) on aluminum-doped zinc oxide (AZO) substrates were fabricated by a single-step aqueous solution method at low temperature. In order to optimize optical quality, the effects of annealing on optical and structural properties were investigated by scanning electron microscopy, X-ray diffraction, photoluminescence (PL), and Raman spectroscopy. We found that the annealing temperature strongly affects both the near-band-edge (NBE) and visible (defect-related) emissions. The best characteristics have been obtained by employing annealing at 400°C in air for 2 h, bringing about a sharp and intense NBE emission. The defect-related recombinations were also suppressed effectively. However, the enhancement decreases with higher annealing temperature and prolonged annealing. PL study indicates that the NBE emission is dominated by radiative recombination associated with hydrogen donors. Thus, the enhancement of NBE is due to the activation of radiative recombinations associated with hydrogen donors. On the other hand, the reduction of visible emission is mainly attributed to the annihilation of OH groups. Our results provide insight to comprehend annealing effects and an effective way to improve optical properties of low-temperature-grown ZnO NRs for future facile device applications.

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“…It is reported [31] that the electrical conductivity in the interfacial contact between graphene and photocatalyst components is vital to the overall photocatalytic H 2 production. In addition, unintentional doping of TiO 2 may happen under annealing at 400 ∘ C [32,33], which can increase the visible-light absorbance of TiO 2 and MWCNT-TiO 2 . Therefore, there exists an optimal ratio of MWCNT to TiO 2 for achieving excellent electrical conductivity in the nanocomposites and significant photoactivity for H 2 evolution [30].…”

Section: Resultsmentioning

confidence: 99%

Multiwalled Carbon Nanotube‐TiO₂ Nanocomposite for Visible‐Light‐Induced Photocatalytic Hydrogen Evolution

Zhang

Fan

et al. 2014

Journal of Nanomaterials

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Multiwalled carbon nanotube- (MWCNT-) TiO2nanocomposite was synthesized via hydrothermal process and characterized by X-ray diffraction, UV-vis diffuse reflectance spectroscopy, field emission scanning electron microscope, thermogravimetry analysis, and N2adsorption-desorption isotherms. Appropriate pretreatment on MWCNTs could generate oxygen-containing groups, which is beneficial for forming intimate contact between MWCNTs and TiO2and leads to a higher thermal stability of MWCNT-TiO2nanocomposite. Modification with MWCNTs can extend the visible-light absorption of TiO2. 5 wt% MWCNT-TiO2derived from hydrothermal treatment at 140°C exhibiting the highest hydrogen generation rate of 15.1 μmol·h−1under visible-light irradiation and a wide photoresponse range from 350 to 475 nm with moderate quantum efficiency (4.4% at 420 nm and 3.7% at 475 nm). The above experimental results indicate that the MWCNT-TiO2nanocomposite is a promising photocatalyst with good stability and visible-light-induced photoactivity.

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Universal photoluminescence evolution of solution-grown ZnO nanorods with annealing: important role of hydrogen donor

Cited by 51 publications

References 42 publications

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

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

Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature

Multiwalled Carbon Nanotube‐TiO₂ Nanocomposite for Visible‐Light‐Induced Photocatalytic Hydrogen Evolution

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Universal photoluminescence evolution of solution-grown ZnO nanorods with annealing: important role of hydrogen donor

Cited by 51 publications

References 42 publications

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

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

Annealing effects on the optical and morphological properties of ZnO nanorods on AZO substrate by using aqueous solution method at low temperature

Multiwalled Carbon Nanotube‐TiO2 Nanocomposite for Visible‐Light‐Induced Photocatalytic Hydrogen Evolution

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Product

Resources

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Multiwalled Carbon Nanotube‐TiO₂ Nanocomposite for Visible‐Light‐Induced Photocatalytic Hydrogen Evolution