Crystalline silicon thin films with porous Si backside reflector (abstract only)

• Published in: Solar energy materials and solar cells 2002-04, Vol.72 (1), p.221-221
• Main Authors: Bilyalov, R., Solanki, C.S., Poortmans, J., Richard, O., Bender, H., Kummer, M., von Känel, H.
• Format: Article
• Language: English
• Subjects: Crystalline materials; Epitaxial growth; Film growth; Light trapping; Multilayers; Plasma enhanced chemical vapor deposition; Porous Si; Porous silicon; Substrates; Thin films; Transmission electron microscopy; X ray diffraction analysis
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/S0927-0248(01)00168-4

Thin film crystalline Si solar cells on cheap Si-based substrates have a large potential in PV technology. Optical light confinement is a very crucial point of such thin film structures. Porous Si (PS) as a perfect light diffuser could be used as a backside reflector if its multi-layer structure would be preserved during the deposition of a thin Si film. That is why low-energy plasma enhanced chemical vapor deposition (LEPECVD) is chosen to deposit a thin Si film on a PS multilayer structure at low temperature and a high deposition rate. This technique allows one to deposit a Si film with an epitaxial quality on the top of PS without destroying its multilayer structure as revealed by high-resolution X-ray diffraction and cross-sectional transmission electron microscopy (TEM). The epilayers of 10 μm are grown at very high deposition rate (around 3 nm/s) at 590°C. TEM-analysis reveals that during the deposition a high density of defects forms at the interface PS/epi-Si and spreads through the whole epilayer. The defect density is decreased when the deposition temperature is increased to 645°C. LEPECVD appears to be an appropriate deposition technique to grow thin Si films on cheap Si based substrates with PS reflector.