Hybrid 0D–2D WS₂-QDs (n)/SnS (p) as Distributed Heterojunctions for Highly Responsive Flexible Broad-Band Photodetectors

Abstract

Even though there are reports on broad-band photodetectors, the issue that remains unaddressed is the low responsivity value while increasing the spectral range. This report demonstrates the development of a distributed heterostructure-based broad-band (UV−vis−NIR) photodetector with WS 2 quantum dots (QDs) randomly placed on tin sulfide nanosheets (WS 2 -QDs/SnS) on a biodegradable cellulose paper substrate. The synergetic effect of visible−NIR light absorbance of SnS and UV light absorbance of WS 2 -QDs is used to get broad-band detection from a UV to NIR region. Metal contacts are fabricated on SnS so that they can efficiently collect the photogenerated charge carriers. Thus, an SnS layer in the device is used as a transport layer for the photogenerated electron−hole pairs in WS 2 -QDs. Further, SnS, being ptype, and WS 2 -QDs, being n-type, create a discontinuous distributed high electric field across the device, which accounts for the effective dissociation of generated electron and hole pairs, increasing the responsivity significantly. Responsivity was found to be 0.655, 0.719, and 0.478 A W −1 under UV, visible (vis), and near-infrared (NIR) regions of the electromagnetic spectrum, respectively. Here, in this report, not only the spectral range is improved but also responsivity is enhanced, which is a significant step ahead in flexible broad-band photodetectors.

Broadband, Ultra-High-Responsive Monolayer MoS2/SnS2 Quantum-Dot-Based Mixed-Dimensional Photodetector

“…Parallel research on increasing the spectral range of photodetector was also done. Various strategies include band gap modulation, surface interface engineering, discrete distribution, novel structure design, mixed-dimensional hybrid, and so on − have been reported to improve the photodetector performance. Despite the continuous development and responsivity improvement of photodetectors, the key factor limiting the performance of the photodetectors is the limited spectral range in the electromagnetic spectrum. − Hence, there is an urgent need to develop a powerful strategy or promising method which not only enhances the photoresponsivity but also extends the spectral range of the photodetector.…”

Plasmonic Au Nanoparticles Coated on ReS2 Nanosheets for Visible-Near-Infrared Photodetectors

“…The ubiquitous metrics used to quantify the performance of a photodetector include responsivity ( R ), specific detectivity ( D *), and EQE. The mathematical expressions for the given quantities are given below: − where I dark , P in , h , I ph, λ, q , S , and c are dark current, intensity of light illuminated, Planck’s constant, photocurrent, the wavelength of light, charge of electron, active area of the device (0.0035 cm 2 ), and speed of light. Photoresponsivity ( R ) indicates the photocurrent generated per unit area under light illumination.…”

A fully printed ultrafast Si/WS2 quantum dot photodetector with very high responsivity over the UV to near-infrared region

“…However, QDs exhibit poor carrier transport compared to conventional semiconductors, which significantly reduces the effectiveness and performance of photodetectors. But heterostructures and composites based on WS 2 quantum dots have demonstrated excellent photodetection performance 23,24 compared to the pristine material, thus providing an avenue to overcome the shortcomings of QDs.…”