Highly Responsive Ultraviolet Sensor Based on ZnS Quantum Dot Solid with Enhanced Photocurrent

Sellan Premkumar,Devaraj Nataraj,T Daniel Thangadurai,Ganapathi Bharathi,Subramaniam Ramya

doi:10.1038/s41598-019-55097-8

Abstract

Detection of visible blind UV radiation is not only interesting but also of technologically important. Herein, we demonstrate the efficient detection of UV radiation by using cluster like ZnS quantum dot solid nanostructures prepared by simple reflux condensation technique. The short-chain ligand 3-mercaptopropionic acid (MPA) involved in the synthesis lead to the cluster like formation of ZnS quantum dots into solids upon prolonged synthesis conditions. The ZnS QD solid formation resulted in the strong delocalization of electronic wave function between the neighboring quantum dots. It increases the photocurrent value, which can be further confirmed by the decrease in the average lifetime values from 64 to 4.6 ns upon ZnS cluster like QD solid formation from ZnS QDs. The ZnS quantum dot solid based UV sensor shows good photocurrent response and a maximum responsivity of 0.31 (A/W) at a wavelength of 390 nm, is not only competitive when compared with previous reports but also better than ZnS and metal oxide-based photodetectors. The device exhibits a high current value under low-intensity UV light source and an on/off ratio of IUV/Idark = 413 at zero biasing voltage with a fast response. Further, photocurrent device has been constructed using ZnS quantum dot solid nanostructures with graphene hybrids as an active layer to improve the enhancement of photoresponsivity.

Highlights

UV-photodetectors received great scientific attention owing to their significant commercial applications including water treatment, defense safety[1], flame detection, and space communication[2,3,4,5]
Like the arrangement of individual atoms can lead to the formation of atomic solids, quantum dot solid can be formed by means of an effective arrangement of quantum dots
For attaining the improved charge carrier extraction and responsivity further, the ZnS quantum dot cluster like nanostructures were hybridized with graphene and used as an active layer for photodetector device[45,46]

Summary

Introduction

UV-photodetectors received great scientific attention owing to their significant commercial applications including water treatment, defense safety[1], flame detection, and space communication[2,3,4,5]. In recent years a number of innovative research work were undergoing in the construction of ZnS nanostructure[29,30,31] based UV-photodetector with different morphologies like ZnS nanobelts[8,23,28,31,32], ZnS nanotubes[27] and ZnS nanowires[33,34], as an active layer These type of one-dimensional[35] nanostructure-based UV photodetectors show relatively low responsivity and slow photoresponse due to low carrier mobility and high surface reactivity. ZnS nanostructures have the bulk bandgap in the UV region making it a perfect choice as an active layer for UV photo-sensing device With this basic knowledge, we have tuned the morphology of ZnS quantum dots to cluster like ZnS QDs solids by prolonging the reaction time. The present paper discusses the methodology used for attaining clusters like nanostructures and their characterization, the photocurrent study under UV light illumination

Methods

Results

Conclusion