Gap states assisted MoO3 nanobelt photodetector with wide spectrum response.

Du Xiang,Wei Chen,Cheng Han,Jialin Zhang

doi:10.1038/srep04891

Abstract

Molybdenum oxides have been widely investigated for their broad applications ranging from electronics to energy storage. Photodetectors based on molybdenum trioxide (MoO3), however, were seldom reported owing to their low conductivity and weak photoresponse. Herein we report a photodetector based on single MoO3 nanobelt with wide visible spectrum response by introducing substantial gap states via H2 annealing. The pristine MoO3 nanobelt possessed low electrical conductance and no photoresponse for nearly all visible lights. The H2 annealing can significantly improve the conductance of MoO3 nanobelt, and result in a good photodetector with wide visible spectrum response. Under illumination of 680 nm light, the photodetector exhibited high responsivity of ~56 A/W and external quantum efficiency of ~10200%. As corroborated by in situ ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy investigations, such strong wide spectrum photoresponse arises from the largely enriched gap states in the MoO3 nanobelt after H2 annealing.

Highlights

Molybdenum oxides have been widely investigated for their broad applications ranging from electronics to energy storage
As corroborated by in situ ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy investigations, such strong wide spectrum photoresponse arises from the largely enriched gap states in the MoO3 nanobelt after H2 annealing
In situ ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) measurements indicate the significant enrichment of gap states in MoO3 after H2 annealing, thereby leading to the excellent photoresponse in the wide visible spectra region

Summary

Introduction

Molybdenum oxides have been widely investigated for their broad applications ranging from electronics to energy storage. We report a photodetector based on single MoO3 nanobelt with wide visible spectrum response by introducing substantial gap states via H2 annealing. As corroborated by in situ ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy investigations, such strong wide spectrum photoresponse arises from the largely enriched gap states in the MoO3 nanobelt after H2 annealing. It has been demonstrated that generating mid-gap states in these wide bandgap semiconductors can extend the photoactive region to visible or even infrared range, and significantly improve the efficiency of the optoelectronic devices and photocatalysts[7,8,9,10]. The MoO3 nanostructures have been heavily investigated as effective photocatalyst in pollution degradation[27,28] Due to their low intrinsic conductivity and weak photoresponse[29], MoO3 based optoelectronic nanodevices are rarely reported. In situ ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS) measurements indicate the significant enrichment of gap states in MoO3 after H2 annealing, thereby leading to the excellent photoresponse in the wide visible spectra region

Methods

Results

Conclusion