Abstract
Graphene and graphene-based materials exhibit exceptional optical and electrical properties with great promise for novel applications in light detection. However, several challenges prevent the full exploitation of these properties in commercial devices. Such challenges include the limited linear dynamic range (LDR) of graphene-based photodetectors, the lack of efficient generation and extraction of photoexcited charges, the smearing of photoactive junctions due to hot-carriers effects, large-scale fabrication and ultimately the environmental stability of the constituent materials. In order to overcome the aforementioned limits, different approaches to tune the properties of graphene have been explored. A new class of graphene-based devices has emerged where chemical functionalisation, hybridisation with light-sensitising materials and the formation of heterostructures with other 2D materials have led to improved performance, stability or versatility. For example, intercalation of graphene with FeCl is highly stable in ambient conditions and can be used to define photo-active junctions characterized by an unprecedented LDR while graphene oxide (GO) is a very scalable and versatile material which supports the photodetection from UV to THz frequencies. Nanoparticles and quantum dots have been used to enhance the absorption of pristine graphene and to enable high gain thanks to the photogating effect. In the same way, hybrid detectors made from stacked sequences of graphene and layered transition-metal dichalcogenides enabled a class of devices with high gain and responsivity. In this work, we will review the performance and advances in functionalised graphene and hybrid photodetectors, with particular focus on the physical mechanisms governing the photoresponse, the performance and possible future paths of investigation.
Highlights
The discovery of graphene [1] and more broadly of atomically thin materials has triggered a wealth of research in optoelectronics [2], plasmonics [3], telecommunications [4], solar energy harvesting [5]and sensing [6]
We focus our attention onto non-destructive techniques which allow the realisation of heterostructures which preserve the high-mobility of graphene field-effect transistors (FETs) and enhance the light absorption of the device
This article presents an overview of the photodetector technologies based on chemically-functionalised graphene and hybrid structures such as graphene/quantum dots (QDs) interfaces and graphene/transition-metal dichalcogenides (TMDs) heterostructures
Summary
The discovery of graphene [1] and more broadly of atomically thin materials has triggered a wealth of research in optoelectronics [2], plasmonics [3], telecommunications [4], solar energy harvesting [5]. The lack of a bandgap and the intrinsic low light absorption of this single layer of carbon atoms poses some challenges for its use in practical applications [10]. Graphene-based light sensors have shown some exceptional performances, spanning from high speed [4] to large linear dynamic range (LDR) [14], and they offer optical transparency and mechanical flexibility needed for future applications in wearable electronics [8]. Whilst functionalisation can be used to efficiently modify the charge carrier dynamics in graphene which in return can lead to enhanced photoresponse, the hybridisation with NPs, TMDs and organic semiconductors boosts the absorption of light, increasing the efficiency of the PDs. After a description of the materials and fabrication techniques, we will focus our attention on the main physical mechanisms responsible for the photodetection in these materials. We will review the most relevant papers which demonstrate their performance, highlighting strong and weak points for each device, as well as their suitability in specific applications
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