Electrical Tuning of Optical Properties of Quantum Dot–Graphene Hybrid Devices: Interplay of Charge and Energy Transfer

Abstract

The combination of semiconductor quantum dots (QD) and single-layer graphene (SLG) can lead to the formation of optoelectronic devices with enhanced sensitivity and can have extensive applications in the field of the photodetector and photovoltaics. The optical properties of the resultant hybrid material are controlled by the interplay of energy transfer between QDs and charge transfer between the QDs and SLG. By studying the steady-state and time-resolved photoluminescence spectroscopy of hybrid QD−SLG devices, we observe a subtle interplay of short-and long-range energy transfer between cadmium selenide (CdSe) QDs in a compact monolayer solid film placed in close proximity to an SLG and the charge transfer from the QD solid to SLG. At larger separation, δ, between the compact monolayer QD and SLG, the emission properties are dominated by mutual energy transfer between the QDs. At relatively smaller separation the emission from QDs, which is strongly quenched, is dominated by charge transfer between QDs and SLG. In addition, we are also able to tune the relative strength of energy and charge transfer by electrostatic doping through the back gate voltage, which provides a novel pathway to tune emission properties of these devices for possible applications as photodetectors, in photovoltaics, and for sensing.

Augmented Optoelectronic Quantum Dot‐Enhanced Heterogeneous IGZO‐Te Photodiode for Artificial Synaptic Image Processing Applications

“…QD solution, with a concentration of 0.2 mg mL −1 , was coated onto the substrate through the spin coating method. [43][44][45][46] Material Characterizations: To measure the thickness and surface morphology of the IGZO-Te-QD heterostructure films, Scanning Electron Microscopy (SEM) (JSM-6700F, HITACHI, 15 V) and Non-contact mode AFM (XE7, Park Systems) was used. PL and Raman spectroscopy (ALPHA300, WITec) with an excitation wavelength of 532 nm laser (Spot size ≈1 μm) were used to determine bandgaps of QDs.…”

Enhancing Carrier Diffusion Length and Quantum Efficiency through Photoinduced Charge Transfer in Layered Graphene–Semiconducting Quantum Dot Devices

“…The monolayer of QDs was transferred onto graphene FET (GrFET) by the well-known Langmuir–Blodgett method. − The pressure is kept constant at 38 mN/m for a particular area during transfer. The corresponding change in surface pressure has been shown in Supporting Information Figure S3.…”

“…The surface to the surface separation between QDs depends on the dielectric ligands attached to them. , By altering the ligand lengths, we can control the surface separation between QDs and QDs to graphene. We have performed a well-known ligand replacement procedure − and chose ligands with smaller lengths attached to the QDs, leading to a more closely packed system.…”

“…Here, we have measured the photoinduced current in three device configurations: Single-layer graphene FET: pristine GrFET. Compact layer of trioctylphosphine oxide (TOPO) capped CdSe QDs on pristine graphene FET [surface to surface separation between QDs and graphene ( d s ) of ∼1.1 nm]: TOPO QD on GrFET. ,, Compact layer of sulfur (Sul)-capped CdSe QDs on pristine GrFET to reduce the separation ( d s ∼ 0.3 nm): Sul-QD on GrFET By changing the ligand length attached to the QDs, we can control the extent of charge transfer between photoexcited QDs and graphene …”

“…52 By changing the ligand length attached to the QDs, we can control the extent of charge transfer between photoexcited QDs and graphene. 45…”