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Optoelectronic devices combining single-layer graphene (SLG) and colloidal semiconducting nanocrystal (NC) heterojunctions have recently gained significant attention as efficient hybrid photodetectors. While most research has concentrated on systems using heavy metal-based semiconductor NCs, there is a need for further exploration of environmentally friendly nanomaterials, such as Cu2−xS. Chemical ligands play a crucial role in these hybrid photodetectors, as they enable charge transfer between the NCs and SLG. This study investigates the photoresponse of an SLG/Cu2−xS NCs heterojunction, comparing the effect of two short molecules—tetrabutylammonium iodide (TBAI) and 3,4-dimethylbenzenethiol (DMBT)—as surface ligands on the resulting structures. We have analysed charge transfer at the heterojunctions between SLG and the Cu2−xS NCs before and after modification with TBAI and DMBT using Raman spectroscopy and transconductance measurements under thermal equilibrium. The photoresponse of two hybrid devices based on three layers of Cu2₋xS NCs, deposited in one case on SLG/Cu2−xS/TBAI (“TBAI-only” device) and in the other on SLG/Cu2−xS/DMBT (“DMBT + TBAI” device), with a TBAI treatment applied, for both, after each layer deposition, has been evaluated under 450 nm laser diode illumination. The results indicate that the TBAI-only device exhibited a significant increase in photocurrent (4 μA), with high responsivity (40 mA/W) and fast response times (<1 s), while the DMBT + TBAI device had lower photocurrent (0.2 μA) and responsivity (2.4 μA), despite similar response speeds. The difference is attributed to DMBT’s π–π interactions with SLG, which enhances electronic coupling but reduces SLG’s mobility and responsivity. 

Abstract Hybrid photodetectors with 2D materials and quantum dots (QDs) offer new opportunities for spectral detection given their high mobilities and spectral tunability, respectively. Herein, the study presents a novel architecture of alternating PbS QDs with graphene monolayers positioned at different depths and with independent contacts. This geometry enables the probing of the photocurrent depth profile and therefore of different spectral bands. The study realizes devices with up to five graphene layers and five QD layers intercalated, using only one type of QDs (Single‐Bandgap devices) with an exciton absorption peak at 920 nm, as well as devices with different types of QDs (Multi‐Bandgap devices) with exciton peaks at 850, 1190, and 1350 nm. Since the absorption depth and photoresponse is wavelength dependent, each graphene has a different spectral response, which opens the path for spectral analysis. As expected, it is observed that top graphene layers have stronger response than deeper graphene layers, especially for short wavelengths. However, for the case of Multi‐Bandgap devices, a negative photoresponse coefficient is even observed for longer wavelengths, showing stronger response for deeper layers than for top layers. This intercalated architecture can be used for compact multispectral photodetection without any diffractive or beam splitting component.