| 摘要 |
PROBLEM TO BE SOLVED: To make possible photoelectric conversion of light at the long wavelength side by installing an SiGe layer having a narrow band gap on the back side of a solar battery cell. SOLUTION: An N<+> type Si diffusion layer 2 is formed on the light receiving surface side of a P type Si substrate 1. A P<+> type Si diffusion layer 3 and a P<+> Si-Ge alloy layer 4 are formed on the back side of the substrate 1. A junction 5 of the back side is formed between the P<+> type Si diffusion layer 3 and the P<+> type Si-Ge alloy layer 4. The band gap of Si is about 1.1eV, and the band gap of Si-Ge alloy layer is about 0.7eV. Thereby, short wavelength light is sufficiently photoelectrically converted by the thin N<+> layer on the front side and Si of the comparatively thick P<-> substrate, and long wavelength light is photoelectrically converted by the SiGe layer on the back side which has a narrow band gap, so that high photoelectric conversion efficiency can be obtained. |
