Crystalline Si photovoltaics benefits from more than half a century of experience in Si microelectronics. The photovoltaic material Si is abundant in the earth’s crust and is environmentally benign. The main obstacle for a wider spread of crystalline silicon photovoltaics is the high cost of crystalline Si wafers that have a typical thickness of 300μm and account for about 50% of the module costs. The reduction of the Si consumption is the driving force for the world-wide increasing interest in the development of thin film modules.

 To make the flexible thin film cells whose thickness is less than 30um, we focus on the stress-induced lift-off process. A special surface conditioning of the substrate permits the transfer of the device layer from a re-usable growth substrate to a low-cost device carrier. Using a monocrystalline Si wafer as the growth substrate permits to fabricate monocrystalline cells. Grain boundaries and their recombination losses are fully avoided. The cost of the Si substrate is not a problem if the substrate wafer is re-used frequently.