Ultrasonic irradiation assisted growth of organic polypyrrole nanospheres reinforced 3D-hierarchical macroporous Ni-foam based high performance broadband photodetector

Most inorganic photodetectors are rigid and have narrow intrinsic bandgap, which severely limits their application in next generation flexible electronics. To overcome this issue, this work reports a flexible, biocompatible, organic-photodetector based on solution processed Ppy nanospheres deposited over 3D-hierarchical macro-porous Ni foam substrate using ultrasonic irradiation technique. The Ni foam substrate is used as buffering layer to bond with organic polypyrrole which has outstanding flexible photoelectric character. Morphological studies reveal the uniform growth of Ppy nanospheres over the porous Ni foam substrate that provides a large surface to volume ratio for efficient interaction of photons. Optical studies show excellent absorption in the UV region and a soret peak in the visible region while structural studies confirm the formation of polypyrrole with C=C stretching and C=N stretching modes. The Ppy/Ni foam-based photodetector displays excellent response with responsivity of 6.5 A/W, 5.4 A/W and 17.3 A/W in the UV, visible and NIR region of the spectrum, respectively for a minimum bias voltage of 1 mV. The spectral detectivity of the device was obtained as 1011 Jones demonstrating a least noise equivalent power. The acquired performance can be attributed to the synergistic effect of photon excitation as well as molecular-phonon vibration upon illumination of light. A maximum EQE of 27.56 was achieved for NIR light owing to the trap-assisted charge carrier tunneling injection from the Ppy/Ni interface. The solution processed Ppy/Ni foam photodetector proves to be a better alternative for broad band photodetection over previously reported organic photodetectors fabricated using sophisticated techniques. The strategy employed here paves new path for synthesis and fabrication of organic photodetectors towards optoelectronic applications.