Abstract
This study demonstrates significant visible light photo-detection capability of pristine ZnO nanostructure thin films possessing substantially high percentage of oxygen vacancies ({V}_{o}{rm{s}}) and zinc interstitials (Z{n}_{i}{rm{s}}), introduced by simple tuning of economical solution method. The demonstrated visible light photo-detection capability, in addition to the inherent UV light detection ability of ZnO, shows great dependency of {V}_{o}{rm{s}} and Z{n}_{i}{rm{s}} with the nanostructure morphology. The dependency was evaluated by analyzing the presence/percentage of {V}_{o}{rm{s}} and Z{n}_{i}{rm{s}} using photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS) measurements. Morphologies of ZnO viz. nanoparticles (NPs), nanosheets (NSs) and nanoflowers (NFs), as a result of tuning of synthesis method contended different concentrations of defects, demonstrated different photo-detection capabilities in the form of a thin film photodetector. The photo-detection capability was investigated under different light excitations (UV; 380~420 nm, white ; λ > 420 nm and green; 490~570 nm). The as fabricated NSs photodetector possessing comparatively intermediate percentage of {V}_{o}{rm{s}} ~ 47.7% and Z{n}_{i}{rm{s}} ~ 13.8% exhibited superior performance than that of NPs and NFs photodetectors, and ever reported photodetectors fabricated by using pristine ZnO nanostructures in thin film architecture. The adopted low cost and simplest approach makes the pristine ZnO-NSs applicable for wide-wavelength applications in optoelectronic devices.
Highlights
Photodetectors have a wide range of applications in many important areas such as; space communication, air quality monitoring, flame monitoring, industrial quality control, optical imaging, optoelectronic circuits, military surveillances etc.[1]
The tuning of morphology of undoped ZnO nanostructures, capable of broadband spectral-response through the combined effect of multiple scattering and formation of Vos and zinc interstitials (Znis), synthesized by the simple solution method would be highly valuable for making an economical photodetector
We found that from the fabricated nanostructures, the NSs photodetector in a thin film form shows a faster rise and decay time both in the ultra violet (UV) and visible spectrum region than that of the co-fabricated NPs and NFs photodetectors, and the ever reported sophisticated single ZnO nanowire based photodetector working only in UV region[24,25,26]
Summary
Photodetectors have a wide range of applications in many important areas such as; space communication, air quality monitoring, flame monitoring, industrial quality control, optical imaging, optoelectronic circuits, military surveillances etc.[1]. Conventional photodetectors employ crystalline semiconductor materials such as; silicon, germanium, gallium arsenide etc In these materials certain issues still need to be addressed; for instance, requirement of high temperature conditions for device fabrication, possibility of blurring, cross talk of optical signals between neighboring pixels[2] and limited freedom in material design. To overcome these problems, studies on inorganic semiconductor nanostructures[3,4] such as; ZnS, InSe, CdS, CdSe etc. The tuning of morphology of undoped ZnO nanostructures, capable of broadband spectral-response through the combined effect of multiple scattering and formation of Vos and Znis, synthesized by the simple solution method would be highly valuable for making an economical photodetector
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