Intercalated Graphene and Colloidal Quantum Dots for Multispectral Photodetection

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.