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Fabrication and characterization of silicon wire solar cells having ZnO nanorod antireflection coating on Al-doped ZnO seed layer.

Baek SH, Noh BY, Park IK, Kim JH - Nanoscale Res Lett (2012)

Bottom Line: The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination.The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering.Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it.

View Article: PubMed Central - HTML - PubMed

Affiliation: Energy Research Division, Daegu Gyeongbuk Institute of Science & Technology (DGIST), 50-1, Sang-Ri, Hyeonpung-Myeon, Dalseong-gun, Daegu, 711-873, South Korea. jaehyun@dgist.ac.kr.

ABSTRACT
In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it.

No MeSH data available.


SEM images of the AZO seed layer and ZnO nanorods. (a, b) The AZO seed layer was grown on bare Si and (c, d) ZnO nanorods were grown on AZO seed layer. (e) X-ray diffraction patterns of Al-doped and undoped ZnO films grown on bare Si by ALD.
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Figure 2: SEM images of the AZO seed layer and ZnO nanorods. (a, b) The AZO seed layer was grown on bare Si and (c, d) ZnO nanorods were grown on AZO seed layer. (e) X-ray diffraction patterns of Al-doped and undoped ZnO films grown on bare Si by ALD.

Mentions: We have synthesized vertically aligned ZnO nanorods with solution methods using two-step procedures. AZO seed layers were deposited with the ALD system followed by the hydrothermal growth of the ZnO nanorods. Figure 2 shows the SEM images of the AZO seed layer and ZnO nanorods using the AZO seed layer grown on a bare Si wafer, respectively. The thickness of the AZO thin layer is approximately 45 nm (Figure 2a). It can be seen that the AZO films with uniform crystal grain size and flat surface morphology can be obtained by the ALD setup. The arrays consisted of ZnO nanorods with diameters of 50 nm, and the lengths of the rods ranged from 800 nm to 900 nm after the growth time of 3 h by hydrothermal synthesis. Panels c and d from Figure 2 depict that the ZnO nanorods were well grown on Si surfaces that permitted vertically aligned nanocrystal growth to the c-axis direction. We also observed that the size of the ZnO nanorods was uniform, and the hexagonal ZnO nanorods demonstrated good crystallinity. The XRD spectra of Al-doped and undoped ZnO thin films grown on Si (100) by ALD are shown in Figure 2e. The major peaks of the ALD-deposited ZnO film appearing at 2θ = 31.87°, 34.45°, and 36.31° were assigned to the (100), (002), and (101) planes of the hexagonal wurzite ZnO phase, respectively. It is clear that the preferred growth direction of the undoped ZnO sample is ZnO (002) at a 2θ peak of approximately 34.45°. After Al doping, a 0.2° peak shift in a diffraction angle of 34.45° from the wurtzite structure to higher values is observed, which is due to the substitution of Al3+ ions for Zn2+ ions in the ZnO lattice during the growth [27]. The ionic radius of Al3+ cation is 0.54 Å, which is smaller than that of Zn2+ cation (0.74 Å). The substitutional doping of Al3+ at the Zn2+ site will lead to a reduction of the lattice parameter in the ZnO phase and then result in the peak shift [28]. More detailed results and discussions of ALD-deposited AZO films are described elsewhere [29].


Fabrication and characterization of silicon wire solar cells having ZnO nanorod antireflection coating on Al-doped ZnO seed layer.

Baek SH, Noh BY, Park IK, Kim JH - Nanoscale Res Lett (2012)

SEM images of the AZO seed layer and ZnO nanorods. (a, b) The AZO seed layer was grown on bare Si and (c, d) ZnO nanorods were grown on AZO seed layer. (e) X-ray diffraction patterns of Al-doped and undoped ZnO films grown on bare Si by ALD.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 2: SEM images of the AZO seed layer and ZnO nanorods. (a, b) The AZO seed layer was grown on bare Si and (c, d) ZnO nanorods were grown on AZO seed layer. (e) X-ray diffraction patterns of Al-doped and undoped ZnO films grown on bare Si by ALD.
Mentions: We have synthesized vertically aligned ZnO nanorods with solution methods using two-step procedures. AZO seed layers were deposited with the ALD system followed by the hydrothermal growth of the ZnO nanorods. Figure 2 shows the SEM images of the AZO seed layer and ZnO nanorods using the AZO seed layer grown on a bare Si wafer, respectively. The thickness of the AZO thin layer is approximately 45 nm (Figure 2a). It can be seen that the AZO films with uniform crystal grain size and flat surface morphology can be obtained by the ALD setup. The arrays consisted of ZnO nanorods with diameters of 50 nm, and the lengths of the rods ranged from 800 nm to 900 nm after the growth time of 3 h by hydrothermal synthesis. Panels c and d from Figure 2 depict that the ZnO nanorods were well grown on Si surfaces that permitted vertically aligned nanocrystal growth to the c-axis direction. We also observed that the size of the ZnO nanorods was uniform, and the hexagonal ZnO nanorods demonstrated good crystallinity. The XRD spectra of Al-doped and undoped ZnO thin films grown on Si (100) by ALD are shown in Figure 2e. The major peaks of the ALD-deposited ZnO film appearing at 2θ = 31.87°, 34.45°, and 36.31° were assigned to the (100), (002), and (101) planes of the hexagonal wurzite ZnO phase, respectively. It is clear that the preferred growth direction of the undoped ZnO sample is ZnO (002) at a 2θ peak of approximately 34.45°. After Al doping, a 0.2° peak shift in a diffraction angle of 34.45° from the wurtzite structure to higher values is observed, which is due to the substitution of Al3+ ions for Zn2+ ions in the ZnO lattice during the growth [27]. The ionic radius of Al3+ cation is 0.54 Å, which is smaller than that of Zn2+ cation (0.74 Å). The substitutional doping of Al3+ at the Zn2+ site will lead to a reduction of the lattice parameter in the ZnO phase and then result in the peak shift [28]. More detailed results and discussions of ALD-deposited AZO films are described elsewhere [29].

Bottom Line: The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination.The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering.Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it.

View Article: PubMed Central - HTML - PubMed

Affiliation: Energy Research Division, Daegu Gyeongbuk Institute of Science & Technology (DGIST), 50-1, Sang-Ri, Hyeonpung-Myeon, Dalseong-gun, Daegu, 711-873, South Korea. jaehyun@dgist.ac.kr.

ABSTRACT
In this study, we have fabricated and characterized the silicon [Si] wire solar cells with conformal ZnO nanorod antireflection coating [ARC] grown on a Al-doped ZnO [AZO] seed layer. Vertically aligned Si wire arrays were fabricated by electrochemical etching and, the p-n junction was prepared by spin-on dopant diffusion method. Hydrothermal growth of the ZnO nanorods was followed by AZO film deposition on high aspect ratio Si microwire arrays by atomic layer deposition [ALD]. The introduction of an ALD-deposited AZO film on Si wire arrays not only helps to create the ZnO nanorod arrays, but also has a strong impact on the reduction of surface recombination. The reflectance spectra show that ZnO nanorods were used as an efficient ARC to enhance light absorption by multiple scattering. Also, from the current-voltage results, we found that the combination of the AZO film and ZnO nanorods on Si wire solar cells leads to an increased power conversion efficiency by more than 27% compared to the cells without it.

No MeSH data available.