New solar cells using Ge dots embedded in Si PIN structures

An attempt to embed stacked Ge dots in the intrinsic layer of Si-based PIN solar cells to improve the device performance was reported. The relationship between structural parameters and photovoltaic properties through systematic variation of the repetition number of staked Ge dots and Si spacer width to separate Ge dots was also discussed. The self-assembled Ge dots were grown via the Stranski-Krastanov growth mode separated by Si spacers, following to a 100-nm Si buffer layer. The external quantum efficiency in the infrared region of the solar cells with and without Ge dots in the intrinsic reqion was shown. The Ge coverage was fixed at 8 monolayers (ML), and the number of repetitions and the spacer layer thickness were systematically changes.