Transfer of monocrystalline silicon films to arbitrary foreign substrates is a promising way for the fabrication of high quality silicon films on foreign substrates, demonstrated by solar cell efficiencies on glass as high as 16.6 % in the past. Transfer technologies also enable the use of flexible substrates. This paper investigates the mechanical stability of the separation layer for two different morphologies. First measurements on the minimum bending radius of unsupported silicon films are presented that allow us to estimate minimum curvatures for flexible monocrystalline devices. Finally, we report the first flexible monocrystalline thin film silicon solar cell of 4 cm2 with an independently confirmed efficiency of 14.6 %.