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

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 WS2 quantum dots (QDs) randomly placed on tin sulfide nanosheets (WS2-QDs/SnS) on a biodegradable cellulose paper substrate. The synergetic effect of visible-NIR light absorbance of SnS and UV light absorbance of WS2-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 WS2-QDs. Further, SnS, being p-type, and WS2-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.