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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: The thickness of amorphous Si layer was designed to be 4 nm, and the thickness of amorphous SiC layer was kept at 2 nm.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

Optical absorption coefficient spectra of Si/SiC multilayers. As-deposited (blue line) and 900 °C annealed samples (black line). The inset is the (αhν)1/2 ~ hν relationship of 900°C annealed sample.
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Figure 4: Optical absorption coefficient spectra of Si/SiC multilayers. As-deposited (blue line) and 900 °C annealed samples (black line). The inset is the (αhν)1/2 ~ hν relationship of 900°C annealed sample.

Mentions: The optical properties of Si/SiC MLs deposited on quartz substrate before and after annealing are studied by measuring the optical transmission spectra and reflection spectra in the spectral range of 200 to 800 nm. The optical absorption coefficient α is calculated and given in Figure 4. It is found that the optical absorption of as-deposited a-Si/SiC MLs is quite high, which is above 105 cm-1 when the wavelength is less than 400 nm. However, the absorption coefficient of 900°C annealed Si QDs/SiC MLs is much higher in the whole visible light region (300 to 800 nm), which indicates that the Si QDs/SiC MLs can strongly absorb the visible light photons, especially in short-wavelength range. Based on the Tauc model, the optical band gap of Si QDs/SiC MLs can be deduced from the linear fitting of (αhν)1/2 ~ hν relationship [21], as shown in the inset of Figure 4. The deduced optical band gap of our MLs after 900°C annealing is 1.48 eV, which is blueshifted compared to that of crystallized Si, which can be attributed to the quantum size effect [22]. In our previous work, we found that the optical band gap of Si QDs/SiC MLs is enlarged with reducing the dot size, which resulted in the blueshift of electroluminescence peaks. We used a modified effective mass approximation (EMA) model to estimate the band gap of Si QDs/SiC MLs instead of infinite barrier model by considering the Coulomb effect and the correlation energy terms [23]. Based on this model, the optical band gap (Egopt) can be expressed as follows:


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)

Optical absorption coefficient spectra of Si/SiC multilayers. As-deposited (blue line) and 900 °C annealed samples (black line). The inset is the (αhν)1/2 ~ hν relationship of 900°C annealed sample.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Optical absorption coefficient spectra of Si/SiC multilayers. As-deposited (blue line) and 900 °C annealed samples (black line). The inset is the (αhν)1/2 ~ hν relationship of 900°C annealed sample.
Mentions: The optical properties of Si/SiC MLs deposited on quartz substrate before and after annealing are studied by measuring the optical transmission spectra and reflection spectra in the spectral range of 200 to 800 nm. The optical absorption coefficient α is calculated and given in Figure 4. It is found that the optical absorption of as-deposited a-Si/SiC MLs is quite high, which is above 105 cm-1 when the wavelength is less than 400 nm. However, the absorption coefficient of 900°C annealed Si QDs/SiC MLs is much higher in the whole visible light region (300 to 800 nm), which indicates that the Si QDs/SiC MLs can strongly absorb the visible light photons, especially in short-wavelength range. Based on the Tauc model, the optical band gap of Si QDs/SiC MLs can be deduced from the linear fitting of (αhν)1/2 ~ hν relationship [21], as shown in the inset of Figure 4. The deduced optical band gap of our MLs after 900°C annealing is 1.48 eV, which is blueshifted compared to that of crystallized Si, which can be attributed to the quantum size effect [22]. In our previous work, we found that the optical band gap of Si QDs/SiC MLs is enlarged with reducing the dot size, which resulted in the blueshift of electroluminescence peaks. We used a modified effective mass approximation (EMA) model to estimate the band gap of Si QDs/SiC MLs instead of infinite barrier model by considering the Coulomb effect and the correlation energy terms [23]. Based on this model, the optical band gap (Egopt) can be expressed as follows:

Bottom Line: The thickness of amorphous Si layer was designed to be 4 nm, and the thickness of amorphous SiC layer was kept at 2 nm.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