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Facile solution growth of vertically aligned ZnO nanorods sensitized with aqueous CdS and CdSe quantum dots for photovoltaic applications.

Luan C, Vaneski A, Susha AS, Xu X, Wang HE, Chen X, Xu J, Zhang W, Lee CS, Rogach AL, Zapien JA - Nanoscale Res Lett (2011)

Bottom Line: Vertically aligned single crystalline ZnO nanorod arrays, approximately 3 μm in length and 50-450 nm in diameter are grown by a simple solution approach on a Zn foil substrate.A thin Al2O3 layer deposited prior to quantum dot anchoring successfully acts as a barrier inhibiting electron recombination at the Zn/ZnO/electrolyte interface, resulting in power conversion efficiency of approximately 1% with an improved fill factor of 0.55.The in situ growth of ZnO nanorod arrays in a solution containing CdSe quantum dots provides better contact between two materials resulting in enhanced open circuit voltage.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong SAR. andrey.rogach@cityu.edu.hk.

ABSTRACT
Vertically aligned single crystalline ZnO nanorod arrays, approximately 3 μm in length and 50-450 nm in diameter are grown by a simple solution approach on a Zn foil substrate. CdS and CdSe colloidal quantum dots are assembled onto ZnO nanorods array using water-soluble nanocrystals capped as-synthesized with a short-chain bifuncional linker thioglycolic acid. The solar cells co-sensitized with both CdS and CdSe quantum dots demonstrate superior efficiency compared with the cells using only one type of quantum dots. A thin Al2O3 layer deposited prior to quantum dot anchoring successfully acts as a barrier inhibiting electron recombination at the Zn/ZnO/electrolyte interface, resulting in power conversion efficiency of approximately 1% with an improved fill factor of 0.55. The in situ growth of ZnO nanorod arrays in a solution containing CdSe quantum dots provides better contact between two materials resulting in enhanced open circuit voltage.

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Structural characterisation of ZnO NRAs. (a) XRD spectra of ZnO nanorods on Zn substrate and of the bare Zn substrate; (b) top-view SEM image of vertically aligned ZnO nanorods; (c) TEM image of a ZnO nanorod; the inset shows the corresponding FFT pattern that identifies the growth direction as the (001) axis; (d) HRTEM image of a ZnO nanorod showing the lattice spacing and confirming the growth direction; and (e) HRTEM image of a ZnO nanorod coated with a approximately 2 nm Al2O3 film prepared by ALD.
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Figure 1: Structural characterisation of ZnO NRAs. (a) XRD spectra of ZnO nanorods on Zn substrate and of the bare Zn substrate; (b) top-view SEM image of vertically aligned ZnO nanorods; (c) TEM image of a ZnO nanorod; the inset shows the corresponding FFT pattern that identifies the growth direction as the (001) axis; (d) HRTEM image of a ZnO nanorod showing the lattice spacing and confirming the growth direction; and (e) HRTEM image of a ZnO nanorod coated with a approximately 2 nm Al2O3 film prepared by ALD.

Mentions: We have modified a previously reported method of growing large-scale, vertically aligned ZnO NRAs on Zn substrates by a one-step solution-based approach [25]. In the simplified method, this process is improved by employing pure water without the use of additives like the previously used ammonia or hydrogen peroxide. Figure 1a shows the XRD pattern of ZnO NRAs grown on Zn foil. All diffraction peaks can be indexed to hexagonal wurtzite ZnO phase (JCPDS card No. 36-1451) except those marked with * which originate from the zinc substrate (JCPDS card No. 04-0831). Morphological characterization by SEM, Figure 1b, indicates the formation of arrays of ZnO NRs with a preferential growth direction nearly perpendicular to the Zn substrate. The nanorods are uniform in length (~3 μm) and possess a characteristic hexagonal cross-section with diameter in the range of approximately 50 to 450 nm. Higher magnification of a single ZnO nanorod by TEM is shown in Figure 1c; the corresponding FFT pattern indicates that the hexagonal ZnO nanorod grows along the [001] direction. The growth direction is further confirmed by high-resolution TEM image, shown in Figure 1d, which exhibits well-resolved fringes in directions parallel and perpendicular to the nanorod axis, further confirming that the ZnO nanorod is single crystalline. The lattice fringe spacing are 0.524 and 0.287 nm, which agree well with the interplanar spacing of the (001) and (100) planes of hexagonal (wurtzite) ZnO crystals. Selected ZnO NRAs were further treated with an Al2O3 coating prepared by 15 cycles of an ALD process. Figure 1e shows conformal Al2O3 deposition with average film thickness approximately 2 nm.


Facile solution growth of vertically aligned ZnO nanorods sensitized with aqueous CdS and CdSe quantum dots for photovoltaic applications.

Luan C, Vaneski A, Susha AS, Xu X, Wang HE, Chen X, Xu J, Zhang W, Lee CS, Rogach AL, Zapien JA - Nanoscale Res Lett (2011)

Structural characterisation of ZnO NRAs. (a) XRD spectra of ZnO nanorods on Zn substrate and of the bare Zn substrate; (b) top-view SEM image of vertically aligned ZnO nanorods; (c) TEM image of a ZnO nanorod; the inset shows the corresponding FFT pattern that identifies the growth direction as the (001) axis; (d) HRTEM image of a ZnO nanorod showing the lattice spacing and confirming the growth direction; and (e) HRTEM image of a ZnO nanorod coated with a approximately 2 nm Al2O3 film prepared by ALD.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211429&req=5

Figure 1: Structural characterisation of ZnO NRAs. (a) XRD spectra of ZnO nanorods on Zn substrate and of the bare Zn substrate; (b) top-view SEM image of vertically aligned ZnO nanorods; (c) TEM image of a ZnO nanorod; the inset shows the corresponding FFT pattern that identifies the growth direction as the (001) axis; (d) HRTEM image of a ZnO nanorod showing the lattice spacing and confirming the growth direction; and (e) HRTEM image of a ZnO nanorod coated with a approximately 2 nm Al2O3 film prepared by ALD.
Mentions: We have modified a previously reported method of growing large-scale, vertically aligned ZnO NRAs on Zn substrates by a one-step solution-based approach [25]. In the simplified method, this process is improved by employing pure water without the use of additives like the previously used ammonia or hydrogen peroxide. Figure 1a shows the XRD pattern of ZnO NRAs grown on Zn foil. All diffraction peaks can be indexed to hexagonal wurtzite ZnO phase (JCPDS card No. 36-1451) except those marked with * which originate from the zinc substrate (JCPDS card No. 04-0831). Morphological characterization by SEM, Figure 1b, indicates the formation of arrays of ZnO NRs with a preferential growth direction nearly perpendicular to the Zn substrate. The nanorods are uniform in length (~3 μm) and possess a characteristic hexagonal cross-section with diameter in the range of approximately 50 to 450 nm. Higher magnification of a single ZnO nanorod by TEM is shown in Figure 1c; the corresponding FFT pattern indicates that the hexagonal ZnO nanorod grows along the [001] direction. The growth direction is further confirmed by high-resolution TEM image, shown in Figure 1d, which exhibits well-resolved fringes in directions parallel and perpendicular to the nanorod axis, further confirming that the ZnO nanorod is single crystalline. The lattice fringe spacing are 0.524 and 0.287 nm, which agree well with the interplanar spacing of the (001) and (100) planes of hexagonal (wurtzite) ZnO crystals. Selected ZnO NRAs were further treated with an Al2O3 coating prepared by 15 cycles of an ALD process. Figure 1e shows conformal Al2O3 deposition with average film thickness approximately 2 nm.

Bottom Line: Vertically aligned single crystalline ZnO nanorod arrays, approximately 3 μm in length and 50-450 nm in diameter are grown by a simple solution approach on a Zn foil substrate.A thin Al2O3 layer deposited prior to quantum dot anchoring successfully acts as a barrier inhibiting electron recombination at the Zn/ZnO/electrolyte interface, resulting in power conversion efficiency of approximately 1% with an improved fill factor of 0.55.The in situ growth of ZnO nanorod arrays in a solution containing CdSe quantum dots provides better contact between two materials resulting in enhanced open circuit voltage.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong SAR. andrey.rogach@cityu.edu.hk.

ABSTRACT
Vertically aligned single crystalline ZnO nanorod arrays, approximately 3 μm in length and 50-450 nm in diameter are grown by a simple solution approach on a Zn foil substrate. CdS and CdSe colloidal quantum dots are assembled onto ZnO nanorods array using water-soluble nanocrystals capped as-synthesized with a short-chain bifuncional linker thioglycolic acid. The solar cells co-sensitized with both CdS and CdSe quantum dots demonstrate superior efficiency compared with the cells using only one type of quantum dots. A thin Al2O3 layer deposited prior to quantum dot anchoring successfully acts as a barrier inhibiting electron recombination at the Zn/ZnO/electrolyte interface, resulting in power conversion efficiency of approximately 1% with an improved fill factor of 0.55. The in situ growth of ZnO nanorod arrays in a solution containing CdSe quantum dots provides better contact between two materials resulting in enhanced open circuit voltage.

No MeSH data available.


Related in: MedlinePlus