Graphene Quantum Dots Decorated Al-doped ZnS for Improved Photoelectric Performance.

Zheng Zhang,Liyang Zhao,Zicong Jiang,Yun Lei,Zhong Ouyang

doi:10.3390/ma11081452

Abstract

Graphene quantum dots (GQDs) decorated Al-doped ZnS composites were prepared using the solvothermal process, and the hydrothermal method was used to prepare GQDs. Various spectroscopic techniques were used to characterize the products, and the results show that Al-ZnS attached GQD composites present lattice fringes that can be assigned to ZnS and GQDs, respectively. The absorption peaks of Al-ZnS/GQDs are red-shifted because of the doping of aluminum and the incorporation of GQDs. The luminescence intensity of Al-ZnS/GQDs shows a downward trend with the addition of GQDs. As the GQD content changes from 0.6 wt % to 1.8 wt %, the photocurrent density achieves a maximum at the addition of 1.2 wt %. The photocurrent of Al-ZnS/GQDs composites are about 700% and 200% of pure ZnS and Al-ZnS, respectively. The results indicate that Al doping can reduce the energy bandgap of ZnS and produce more photogenerated electrons. The photogenerated electrons from Al-ZnS can be extracted and transferred to GQDs, which act as conducting materials to decrease the recombination rate and improve the photogenerated electron-transfer.

Highlights

ZnS is one of the promising direct-band semiconductors and is extensively investigated due to its wide bandgap, large exciting binding energy, and superior photoelectric characteristics [1,2,3,4]
Reddy et al prepared the ZnS:Al nanostructures, and investigated the variation of the morphological, structural, optical, and photoluminescence properties caused by Al doping
The dry sample was dissolved in distilled water through ultrasonication to obtain a homogeneous mixture

Summary

Introduction

ZnS is one of the promising direct-band semiconductors and is extensively investigated due to its wide bandgap, large exciting binding energy, and superior photoelectric characteristics [1,2,3,4]. When the light was irradiated on the surface of ZnS, the photogenerated electrons were limited by a broad bandgap of ZnS semiconductor. Al-doped ZnS nanowires with large gain-bandwidth and high responsivity [9]. Reddy et al prepared the ZnS:Al nanostructures, and investigated the variation of the morphological, structural, optical, and photoluminescence properties caused by Al doping. Dole et al used a hydrothermal method to synthesize Al doped ZnS nanorods, and the energy bandgap of Al doped ZnS shows a red shift [11]

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Results

Conclusion