Flexible photodiodes have become a focus of current research because they may offer unique applications in various new areas requiring lightweight, flexible, and mechano‐resistive features. In this study, InP quantum wires have been prepared via microwave approach with a mean diameter of 7 nm. The morphology and elemental composition of the prepared InP quantum wires were characterized using the scanning electron microscope (SEM), the energy dispersive X-ray spectroscopy (EDS), the transmission electron microscopy (TEM), and the selected area of electron diffraction (SAED). The crystal structure was studied using the X-ray diffractometer (XRD). The crystallite size and the lattice strain were estimated using the size-strain model. The Raman scattering spectroscopy and photoluminescence measurements reveal the strong quantum confinement of the InP QW. A flexible hybrid InP QW/PC71BM heterostructure photodiode was constructed on a PET substrate. The developed photodiode exhibits high photoresponsivity and fast detection of incident laser photons. The charge transport mechanism based on the band-offset alignment diagram was discussed.