A Wide Band Gap Boron-doped Microcrystalline Silicon Film Obtained with VHF Glow Discharge Method
- PDF / 123,675 Bytes
- 4 Pages / 595 x 842 pts (A4) Page_size
- 33 Downloads / 195 Views
J15.5.1
A wide band gap Boron-doped microcrystalline silicon film obtained with VHF glow discharge method Zhu feng♣, Zhao ying, Wei changcun, Zhang xiaodan, Gao yantao，Sun jian, Geng xinhua Institute of photo-electronics thin film devices and technique of Nankai University Key Laboratory of photo-electronics thin film devices and technique of Tianjin Key Laboratory of Opto-electronic Information Science and Technology，Tianjin, China
Abstract: A wide bandgap microcrystalline silicon film for the window layer of microcrystalline silicon thin film solar cells was obtained with very high frequency (VHF) glow discharge technology. The material was deposited on corning 7059 substrate at about 170℃.When H2/SiH4 was more than 100, Raman spectra showed that this material was highly crystallized, and no peak correlation with amorphous silicon was observed. This material showed strong n type before any intentional doping. We considered that the unintentional doping of oxygen and unpurified gases. The doping performance of this material was investigated by introducing B2H6 into the reacting gas. As increasing the rate of B2H6/SiH4 from zero to 0.5%, the conductivity changed from 10-1 S.cm-1 (n type) to 10-8 S.cm-1 dramatically and than backed to 10-1 S.cm-1 (p type), which indicated that this material had excellent doping ability. Raman spectra also showed that the microstructure of these materials did not change obviously in this doping range. We gained the p-uc-Si:H film with thickness less than 30nm, and the conductivity was more than 10-2 S.cm-1, and crystalline volume fraction no less than 40%, the Egopt could be wider than 2.10eV. Using this p window layer in microcrystalline silicon solar cells with no ZnO rear reflection, the conversion efficiency was 8.30% (Voc=0.531V, Jsc=24.66mA/cm2, FF=63.41% ). Keywords:
VHF-GD microcrystalline silicon
solar cell
1. Introduce Microcrystalline silicon (uc-Si:H) deposited at a low temperature (100 (showed in Fig.3 insert). The firstly increase of conductivity with hydrogen dilution results from increased doping efficiency with high crystallization. In our experiment, the B2H6/SiH4 was fixed 0.5%. As the crystallization increased more, some of B2H6 in material became impurity, which made the conductivity of material decrease. At the time, as the crystallization increased, the voids in materials also increased. Because of those two factors, the conductivity of material decreased when H2/SiH4 was more than 100. In our experiment, hydrogen dilution ration increased from 66.67 to 200, the SiH*/Hα* decreased monotonously from about 1.45 to about 1.2 (Fig.4). As the hydrogen dilution ratio increased, the Hα* in plasma increased, which indicated that the atomic hydrogen in plasma increased. Now, it was known that the atomic hydrogen promoted crystallization [5]. When the hydrogen dilution ration was between 100 and 120, in plasma the SiH*/Hα* was 1.35 to 1.25, the crystalline volume fraction was about 60%, and the dark conductivity was highest.. 4 8 2 .4 8
5 0 6 .7 4
intensity (a.u.)
Data Loading...
