Spectral Response Modelling of Multilayer Graphene/Quantum Dot Heterostructures

Abstract

Multispectral photodetection is crucial for many optoelectronic applications, such as telecommunication and biomedical imaging. A multilayer heterostructure device with multiple layers of graphene (Gr) and photosensitizers of different bandgaps (e.g., Quantum Dots (QDs)) can be used for multispectral photodetection with a reduced device footprint. We demonstrate a spectral response model of multilayer Gr/QD heterostructure systems, simulating the photocurrents collected by each graphene layer with the illumination light source as the input. We observe matching trends in the photocurrent spectral response in both the experimental data and modelled data of single-junction Gr/QD devices with varying QD thicknesses and device configurations, suggesting our model fit well with experiment. In addition, our model simulates the spectral response of the double-junction multilayer Gr/QD heterostructure device with the layer sequence of Gr/ZnO/SiO₂/PbS QDs/Gr. When compared to experimental data of the same device, our model captures the key photocurrent features, with the Gr/ZnO junction showing large photoresponse at UV wavelengths and the Gr/QDs junction showing photoresponse at a broad range of wavelengths, distinguishing photons in three spectral bands (500 nm or less, 500–1200 nm, and beyond 1200 nm). Our model demonstrates the potential to simulate the spectral response of a layered optoelectronic device, enabling device design and optimization.