A low-cost and complexity-free demonstration of two relatively fast ultraviolet (UV) detectors based on ZnO nanosheets are reported in this letter for the first time. Highly crystalline ZnO nanosheets have been synthesized by a sonochemical method. The proposed UV detectors were fabricated through coating the synthesized materials on Cu electrodes. Experimentally obtained responsivity, detectivity, absorption, and I-V characteristics along with the quantum efficiency are reported. Comparison of the conventional ZnO photo-sensors with nanoparticle-based ones reveals that the proposed nanosheets photosensors have faster response time in the UV region, which might be attributed to low density of defect states (created during synthesis process) on nanosheets surfaces.
Solution-processed ultraviolet photodetectors based on passivated and unpassivated zinc oxide (ZnO) nanorods, in which the ZnO nanoparticles are synthesized by a hydrothermal method, are demonstrated and characterized. Photoconductive photodetectors fabricated using simple solution processing have recently been shown to exhibit high gains and outstanding sensitivities. One ostensible disadvantage of exploiting photoconductive gain is that the temporal response is limited by the release of carriers from trap states. Herein, specific chemical species are introduced onto the surfaces of ZnO nanoparticles to produce desired trap states with a carefully selected lifetime. Compared with conventional photodetectors based on ZnO nanoparticles, the proposed UV photodetectors have much higher photoresponses and faster response times in the UV region. The photoconductive gain of the fabricated photodetectors varies from 26.83 to 2.32×10(2) for passivated samples, which indicates high gain. The best temporal response for the fabricated detectors is 34 ms rise time and 132 ms decay time for ZnO nanoparticles passivated by hexamethylenetetramine.
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