Ultrasensitive Flexible Ultraviolet Detectors Based on Electrochemically Deposited ZnO Microspheres Synthesized by the Assembly of Nanoplatelets

Zinc oxide microspheres synthesized by the assembly of nanoplatelets have been deposited on seeded polycarbonate substrates using the electrochemical deposition technique with the assistance of glycerol. An electrochemical cell with platinum mesh as anode and the seeded substrates as cathode was employed to deposit ZnO microspheres. A computer-controlled potentiostat was used to supply sufficient current for the growth of ZnO nanoplatelets. Zinc chloride was used as a Zn source, and glycerol was applied to assist in the formation of microspheres. The average diameter of formed microspheres was 4 mu m, and the average size of nanoplatelets that formed the microspheres was a few nanometers. The morphology of the nanostructures indicated the formation of ZnO nanoplatelets with various orientations, which can significantly increase the entrapment of incident photons. X-ray diffraction analysis showed a dominant peak related to (002) as a reflection corresponding to the hexagonal ZnO structure. The enhanced photoluminescence (PL) intensity revealed improvement in the lightcapturing ability due to the multiple scattering of light in the nanostructures. The quantum confinement phenomenon in the ZnO crystallites was evident from the blue shift of the PL peak position. A flexible photodetector was fabricated using the metallization of ZnO nanostructures to investigate the capability of ZnO microspheres in light sensing. The optoelectrical properties of fabricated devices were tested under ultraviolet radiation. The devices based on ZnO microspheres exhibited high sensitivity to the incident photons and showed stable photoelectric behavior under various bending conditions.