Abstract
Phosphorus-doped Si nanocrystals embedded in amorphous SiC (Si NCs:SiC) films were fabricated by annealing phosphorus-doped Si-rich amorphous SiC materials at 900°C to get n-type Si NCs/p-Si heterojunction for photovoltaic device applications. The film compositions and the microstructure were characterized by X-ray photoelectron spectra and Raman scattering technique. After phosphorus doping, the dark conductivity can reach to be as high as 48 S/cm which is increased by six orders of magnitude compared with the un-doped one, while the bandgap keeps almost unchanged around 2.14 eV. The improved device performance was confirmed with the fill factor of 58% and the power conversion efficiency of 6.11%, which can be attributed to the good conductivity of phosphorus-doped Si NCs and the improved rectification characteristics of heterojunction structures.
Highlights
Si nanocrystals (Si NCs) embedded in amorphous dielectric host matrix have attracted much attention since they can be potentially applied in many kinds of nano-electronic and opto-electronic devices, such as Si-based light source, non-volatile memories, biosensors and generation of solar cells.1–6 It was proposed that the spectral response range can be extended by using Si NCs embedded in SiC host matrix (Si NCs) films and the corresponding power conversion efficiency can exceeds the so-called Shockly-Quessier limit.7,8 it is proposed to use Si NCs film as a window layer to get the heterojunction solar cells since it can let the most of incident light pass through and absorbed by the bottom Si wafers due to its large optical band gap (>2.0eV)
Amorphous SiC films and Si NCs embedded in amorphous SiC matrix have poor conduction property and it is highly desired to get Si NCs embedded in SiC host matrix (Si NCs:SiC) materials with good conductivity at a suitable bandgap
In order to further increase the conductivity of Si NCs:SiC films, phosphorus doping in Si NCs was performed, and it was found that the room-temperature conductivity can reach as high as 630 S/cm at the annealing temperature exceeding 1000◦C.25
Summary
Si nanocrystals (Si NCs) embedded in amorphous dielectric host matrix (like SiO2, SiC and SiNx) have attracted much attention since they can be potentially applied in many kinds of nano-electronic and opto-electronic devices, such as Si-based light source, non-volatile memories, biosensors and generation of solar cells. It was proposed that the spectral response range can be extended by using Si NCs films and the corresponding power conversion efficiency can exceeds the so-called Shockly-Quessier limit. it is proposed to use Si NCs film as a window layer to get the heterojunction solar cells since it can let the most of incident light pass through and absorbed by the bottom Si wafers due to its large optical band gap (>2.0eV). Si nanocrystals (Si NCs) embedded in amorphous dielectric host matrix (like SiO2, SiC and SiNx) have attracted much attention since they can be potentially applied in many kinds of nano-electronic and opto-electronic devices, such as Si-based light source, non-volatile memories, biosensors and generation of solar cells.. Si NCs embedded in SiO2 host matrix were prepared in photovoltaic devices and the Si NCs/crystalline Si heterojunction solar cells with power conversion efficiency of 10% were reported.. In order to further increase the conductivity of Si NCs:SiC films, phosphorus doping in Si NCs was performed, and it was found that the room-temperature conductivity can reach as high as 630 S/cm at the annealing temperature exceeding 1000◦C.25. We fabricated phosphorus-doped Si NCs:SiC films by annealing Si-rich amorphous SiC samples with relatively high Si/C composition ratio at the moderate temperature (900◦C). The photovoltaic properties are observed under the illumination with AM1.5 solar simulator, and the power conversion efficiency is about 6.11% which is significantly improved compared to that of un-doped reference device
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