Graphene and PbS quantum dot hybrid vertical phototransistor

Abstract

A field-effect phototransistor based on a graphene and lead sulfide quantum dot (PbS QD) hybrid in which PbS QDs are embedded in a graphene matrix has been fabricated with a vertical architecture through a solution process. The n-type Si/SiO substrate (gate), Au/Ag nanowire transparent source electrode, active layer and Au drain electrode are vertically stacked in the device, which has a downscaled channel length of 250 nm. Photoinduced electrons in the PbS QDs leap into the conduction band and fill in the trap states, while the photoinduced holes left in the valence band transfer to the graphene and form the photocurrent under biases from which the photoconductive gain is evaluated. The graphene/QD-based vertical phototransistor shows a photoresponsivity of 2 × 10 A W, and specific detectivity up to 7 × 10 Jones under 808 nm laser illumination with a light irradiance of 12 mW cm. The solution-processed vertical phototransistor provides a new facile method for optoelectronic device applications.

Improved Charge Extraction Beyond Diffusion Length by Layer‐by‐Layer Multistacking Intercalation of Graphene Layers inside Quantum Dots Films

“…Herein, we introduce a novel architecture based on multiple intercalated layers of chemical vapor deposition (CVD) graphene (Gr) monolayers inside a PbS-QD film that overcomes the limitation that diffusion length imposes on the thickness. Single junction [9][10][11][12][13][14] and mixed [15,16] Gr/QD hybrid devices have previously demonstrated high photoresponsivity (PR) combining QDs for light absorption and graphene for efficient charge transport. However, the charge transfer from QDs to Gr for such single-junction (bottom graphene) configuration is still limited by the short L D of QDs.…”

Infrared tunable, two colour-band photodetectors on flexible platforms using 0D/2D PbS–MoS2 hybrids

“…On the other hand, several intriguing properties of leadchalcogenide (PbX) nanocrystals (NCs), such as tunable infrared (IR) absorption owing to the quantum connement and relatively larger excitonic Bohr radius, have inspired researchers to incorporate them into 2D materials to achieve higher efficiency with an extended absorption edge in the solar spectrum. Recently, hybrid graphene/PbS quantum dot (QD) phototransistors, 15,16 PbS/CNT nanohybrids 17 and PbS/ MoX 2 [18][19][20] phototransistors have been demonstrated as promising infrared-photovoltaic devices. However, the synthesis of PbS QDs for device fabrication involved complicated and hazardous chemical pathways using different reducing agents, stabilizing agents, eco-hazard sulfur sources and a complex lithography process, limiting their widespread applications.…”

π–π Interactions Mediated Pyrene Based Ligand Enhanced Photoresponse in Hybrid Graphene/PbS Quantum Dots Photodetectors

“…[ 9–13 ] Recently, hybrid photoconductive detectors, combining QDs as light absorbers and photocarrier generators with graphene or other 2D materials as charge collectors, have attracted great interest due to their ultrahigh gain and high responsivity (10 7 A W −1 ), enabling high‐sensitivity and gate‐tunable photodetection. [ 14–27 ] Recent advances in hybrid photodetectors combining 2D materials and PbS or other QDs are summarized in Table S1 in Supporting Information. In graphene/PbS QD based photodetectors, the band offset at the graphene/QD junction induces a built‐in potential that keeps the photogenerated electrons in the QDs and transfers photo‐holes to graphene producing a photogating effect, leading to a change of carrier density and a photocurrent under the bias voltage V SD across graphene, as shown in Figure a.…”