A mechanically flexible, transparent, rectifying and photosensitive organic-inorganic heterogeneous p-n junction is demonstrated on a plastic substrate. Hexagonally patterned n-type single-crystalline silicon nanomembrane (SiNM), created from silicon-on-insulator (SOI) wafer, was complementally combined with a p-type pentacene layer to form a heterogeneous p-n junction. Excellent rectifying characteristics were obtained from the heterogeneous p-n diode. The diode also exhibits high photosensitivity at visible wavelengths with a photo-to-dark current ratio exceeding four orders, a responsivity of 0.94 mA/W and an external quantum efficiency of 21.9% at 633 nm wavelength. Over 75% peak transmittance in the visible spectrum was measured from the heterogeneous multilayer junction on a thick plastic substrate. Excellent mechanical bending characteristics were observed with up to 1.08% of strain applied to the diode. These results suggest that organic-inorganic heterogeneous integration could be a viable strategy to overcome the intrinsic limits of each individual material and thus enable a number of novel multifunctional applications.