Advances in monocrystalline Si thin film solar cells by layer transfer

The transfer of monocrystalline Si films enables the fabrication of efficient thin film solar cells on glass or plastic foils. Chemical vapor deposition serves to epitaxially deposit Si on quasi-monocrystalline Si films obtained from thermal crystallization of a double-layer porous Si film on a Si wafer. A separation layer that forms during this crystallization process allows one to separate the epitaxial layer on top of the quasi-monocrystalline film from the starting Si wafer after solar cell processing. Independently confirmed thin film solar cell efficiencies are 15.4% and 16.6% for thin film solar cells transferred to a glass superstrate with a total Si film thickness of 24.5 and 46.5 μm, respectively, and a cell area of 4 cm2. Device simulations indicate an efficiency potential above 20%.