Progress in the development of high-conversion-efficiency a-Si/μc-Si tandem solar module using μc-Si thin film with high deposition rate on Gen. 5.5 large-area glass substrate
The technology to make high-quality, high-reliability solar modules with a high deposition rate for μc-Si thin-film is a problem for the industrialization of low-cost, high-conversion-efficiency a-Si/μc-Si tandem structure solar modules. Sanyo has solved this problem by developing an original CVD technique called Localized Plasma Confinement CVD and a new evaluation method for μc-Si thin film. A stabilized conversion efficiency of 10.0% was achieved for an a-Si/μc-Si tandem structure solar module, and a deposition rate of 2.4 nm/s for μc-Si thin-film was attained on a Gen. 5.5 full-size glass substrate. To obtain a higher conversion-efficiency a-Si/μc-Si tandem structure solar module, fundamental studies of μc-Si thin-film have been performed, and a stabilized conversion efficiency of 10.5% (Initial solar module conversion efficiency: 12.0%) has been achieved on a large-area glass substrate. Furthermore, in the study of this development, the highest stabilized conversion efficiency of 12.0% (Initial conversion-efficiency: 13.5%) was attained. Module reliability tests confirmed by IEC 61646 Ed. 2 revealed that the performance of the module is adapted. These high-performance a-Si/μc-Si tandem structure solar modules were prepared by using the knowledge of our thin-film and module technologies.
Correlation between Microstructure and Photovoltaic Performance of Polycrystalline Silicon Thin Film Solar Cells
Intrinsic polycrystalline silicon (poly-Si) thin films have been prepared by plasma enhanced chemical vapor deposition at a very high excitation frequency (100 MHz) for the development of p–i–n junction solar cells. The correlation between poly-Si microstructure and photovoltaic performance of poly-Si solar cells has been investigated as a function of deposition parameters such as deposition pressure, SiH4 flow rate and SiH4 concentration. It is found that the poly-Si microstructure including crystalline volume fraction, Xc, and crystallographic orientation is closely related to the atomic hydrogen flux during film growth, which is evidenced by plasma diagnostics in the in situ measurement of optical emission spectroscopy. Basically, with an increase in Xc, open circuit voltage tends to decrease, while poly-Si with Xc > 50% and (220) preferential orientation is essential for high short circuit current. Based on these results, the role of poly-Si microstructure in the photovoltaic performance of poly-Si solar cells is discussed.
Optical properties of amorphous SixGe1−x(H) alloys prepared by R.F. Glow discharge
Amorphous alloys of Si and Ge have been prepared over the entire composition range by r.f. plasma decomposition of mixed gases of SiH4 and GeH4. The optical absorption edge is found to have a linear dependence on alloy composition given by: Eg = 0.95 + 0.70x (eV).