Discretely distributed 1D V2O5 nanowires over 2D MoS2 nanoflakes for an enhanced broadband flexible photodetector covering the ultraviolet to near infrared region

Abstract

Although most reports on photodetectors focus on improving the responsivity in one region of the electromagnetic spectrum by fabricating hybrid 2D materials, the main issue still remains unaddressed, which is the inability to absorb the wide range of the electromagnetic spectrum. Most photodetectors comprise p–n heterojunctions, where one of the materials is responsible for absorbance, and having metal contacts of p and n type allows for the effective separation of photogenerated carriers. But for a broadband photodetector, both the materials of the heterojunction should participate in the absorbance. In such a case, metal contacts of p and n type will trap either the photogenerated electrons or holes, which leads to the failure of the device. In this work, discrete distribution of 1D V₂O₅ nanowires over 2D MoS₂ and metal contacts on MoS₂ combinedly enables the device to absorb from the ultraviolet to near infrared region (365 nm to 780 nm), wherein V₂O₅ is responsible for UV-visible absorption and MoS₂ absorbs in the visible–NIR region. Furthermore, taking advantage of local heterojunctions of MoS₂–V₂O₅ for the effective separation of photogenerated carriers enables efficient charge transfer, faster electron transfer rate and highly responsive photodetection. The responsivity of the fabricated device was calculated to be 41.5 mA W⁻¹, 65.1 mA W⁻¹ and 29.4 mA W⁻¹ for UV, visible and NIR illumination, suggesting the device to be more responsive in the visible region and the device was found to be comparable with photodetectors fabricated using sophisticated cleanroom techniques. This method provides a new strategy for improving the absorbance range of photodetectors by the discrete distribution of 1D materials over 2D materials, which will find tremendous potential applications in the fields of optoelectronics, sensors and photodetectors.