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Enhanced photovoltaic property by forming p-i-n structures containing Si quantum dots/SiC multilayers.

Cao Y, Lu P, Zhang X, Xu J, Xu L, Chen K - Nanoscale Res Lett (2014)

Bottom Line: Transmission electron microscopy observation revealed the formation of Si QDs after 900°C annealing.The optical properties of the Si QDs/SiC multilayers were studied, and the optical band gap deduced from the optical absorption coefficient result is 1.48 eV.The cell had the open circuit voltage of 532 mV and the power conversion efficiency (PCE) of 6.28%. 81.07.Ta; 78.67.Pt; 88.40.jj.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Laboratory of Solid State Microstructures and School of Electronic Science and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.

ABSTRACT

Unlabelled: Si quantum dots (Si QDs)/SiC multilayers were fabricated by annealing hydrogenated amorphous Si/SiC multilayers prepared in a plasma-enhanced chemical vapor deposition system. The thickness of amorphous Si layer was designed to be 4 nm, and the thickness of amorphous SiC layer was kept at 2 nm. Transmission electron microscopy observation revealed the formation of Si QDs after 900°C annealing. The optical properties of the Si QDs/SiC multilayers were studied, and the optical band gap deduced from the optical absorption coefficient result is 1.48 eV. Moreover, the p-i-n structure with n-a-Si/i-(Si QDs/SiC multilayers)/p-Si was fabricated, and the carrier transportation mechanism was investigated. The p-i-n structure was used in a solar cell device. The cell had the open circuit voltage of 532 mV and the power conversion efficiency (PCE) of 6.28%.

Pacs: 81.07.Ta; 78.67.Pt; 88.40.jj.

No MeSH data available.


Related in: MedlinePlus

Raman spectra of samples. As-deposited Si/SiC multilayers (black line) and 900°C annealed Si/SiC multilayers (red line).
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Figure 1: Raman spectra of samples. As-deposited Si/SiC multilayers (black line) and 900°C annealed Si/SiC multilayers (red line).

Mentions: Figure 1 shows the Raman spectra of as-deposited and 900°C annealed multilayered samples. It is noted that only one broad band centered at 480 cm-1 exists in the as-deposited sample, which is attributed to the transverse optical (TO) mode of amorphous Si-Si bonds. However, an intense peak at 517 cm-1 associated with crystallized Si TO mode appears for 900°C annealed sample, which indicates that the amorphous Si layers have been crystallized to form nano-crystallized Si. In order to estimate the crystallinity ratio and size of Si QDs, we fitted the Raman spectrum via the Gaussian deconvolution by three components, which is located at 480, 510, and 520 cm-1. The crystallinity ratio (Xc) is figured out as 49.5% by integrated Gaussian peaks of 520 and 480 cm-1[19]. The average size of Si crystals is about 4.8 nm, according to the phonon confinement model [20], which indicates the formation of nano-crystalline Si quantum dots.The cross-sectional TEM measurements were performed to further characterize the multilayered structures before and after annealing. Figure 2 is the cross-sectional TEM image of as-deposited a-Si (4 nm)/a-SiC (2 nm) MLs. The layered structures and smooth interfaces of Si/SiC can be clearly identified. The thickness of a-SiC sublayer is 1.9 nm and the thickness of a-Si sublayer is 4.2 nm, respectively, which is very close to the pre-designed value estimated from the deposition rate. Figure 3a shows the cross-sectional TEM image of Si QDs/SiC MLs after 900°C annealing. The periodically layered structures are well kept and the interfaces are still smooth and abrupt. The total thickness of the Si QDs/SiC MLs is about 40 nm. The formation of Si QDs in a-Si layers can be identified in the high-resolution TEM image. As given in Figure 3b, the average size is about 5 nm, which is well agreement with the Raman result. As indicated in the inset of Figure 3b, the crystalline interplanar spacing is 0.31 nm of formed Si QDs, which suggests the Si (111) crystalline faces.


Enhanced photovoltaic property by forming p-i-n structures containing Si quantum dots/SiC multilayers.

Cao Y, Lu P, Zhang X, Xu J, Xu L, Chen K - Nanoscale Res Lett (2014)

Raman spectra of samples. As-deposited Si/SiC multilayers (black line) and 900°C annealed Si/SiC multilayers (red line).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4256967&req=5

Figure 1: Raman spectra of samples. As-deposited Si/SiC multilayers (black line) and 900°C annealed Si/SiC multilayers (red line).
Mentions: Figure 1 shows the Raman spectra of as-deposited and 900°C annealed multilayered samples. It is noted that only one broad band centered at 480 cm-1 exists in the as-deposited sample, which is attributed to the transverse optical (TO) mode of amorphous Si-Si bonds. However, an intense peak at 517 cm-1 associated with crystallized Si TO mode appears for 900°C annealed sample, which indicates that the amorphous Si layers have been crystallized to form nano-crystallized Si. In order to estimate the crystallinity ratio and size of Si QDs, we fitted the Raman spectrum via the Gaussian deconvolution by three components, which is located at 480, 510, and 520 cm-1. The crystallinity ratio (Xc) is figured out as 49.5% by integrated Gaussian peaks of 520 and 480 cm-1[19]. The average size of Si crystals is about 4.8 nm, according to the phonon confinement model [20], which indicates the formation of nano-crystalline Si quantum dots.The cross-sectional TEM measurements were performed to further characterize the multilayered structures before and after annealing. Figure 2 is the cross-sectional TEM image of as-deposited a-Si (4 nm)/a-SiC (2 nm) MLs. The layered structures and smooth interfaces of Si/SiC can be clearly identified. The thickness of a-SiC sublayer is 1.9 nm and the thickness of a-Si sublayer is 4.2 nm, respectively, which is very close to the pre-designed value estimated from the deposition rate. Figure 3a shows the cross-sectional TEM image of Si QDs/SiC MLs after 900°C annealing. The periodically layered structures are well kept and the interfaces are still smooth and abrupt. The total thickness of the Si QDs/SiC MLs is about 40 nm. The formation of Si QDs in a-Si layers can be identified in the high-resolution TEM image. As given in Figure 3b, the average size is about 5 nm, which is well agreement with the Raman result. As indicated in the inset of Figure 3b, the crystalline interplanar spacing is 0.31 nm of formed Si QDs, which suggests the Si (111) crystalline faces.

Bottom Line: Transmission electron microscopy observation revealed the formation of Si QDs after 900°C annealing.The optical properties of the Si QDs/SiC multilayers were studied, and the optical band gap deduced from the optical absorption coefficient result is 1.48 eV.The cell had the open circuit voltage of 532 mV and the power conversion efficiency (PCE) of 6.28%. 81.07.Ta; 78.67.Pt; 88.40.jj.

View Article: PubMed Central - HTML - PubMed

Affiliation: National Laboratory of Solid State Microstructures and School of Electronic Science and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.

ABSTRACT

Unlabelled: Si quantum dots (Si QDs)/SiC multilayers were fabricated by annealing hydrogenated amorphous Si/SiC multilayers prepared in a plasma-enhanced chemical vapor deposition system. The thickness of amorphous Si layer was designed to be 4 nm, and the thickness of amorphous SiC layer was kept at 2 nm. Transmission electron microscopy observation revealed the formation of Si QDs after 900°C annealing. The optical properties of the Si QDs/SiC multilayers were studied, and the optical band gap deduced from the optical absorption coefficient result is 1.48 eV. Moreover, the p-i-n structure with n-a-Si/i-(Si QDs/SiC multilayers)/p-Si was fabricated, and the carrier transportation mechanism was investigated. The p-i-n structure was used in a solar cell device. The cell had the open circuit voltage of 532 mV and the power conversion efficiency (PCE) of 6.28%.

Pacs: 81.07.Ta; 78.67.Pt; 88.40.jj.

No MeSH data available.


Related in: MedlinePlus