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Nanohybrids consisting of quantum dots and graphene (QD/graphene) provides a unique scheme to design quantum sensors. The quantum confinement in QDs enables spectral tunability, while that in graphene provides superior photocarrier mobility. The combination of them allows for broadband light absorption and high photoconduction gain that in turn leads to high photoresponsivity in QD/Gr nanohybrid photodetectors. Since the first QD/graphene photodetector was reported in 2012, intensive research has been conducted on this topic. In this paper, a review of the recent progress made on QD/Gr nanohybrid photodetectors will be provided. Among many applications, there will be a particular focus on broadband and flexible photodetectors, which make use of the inherent advantages of the QD/Gr nanohybrids. The remaining challenges and future perspectives will be discussed in this emerging topic area. 

Abstract Nanohybrids consisting of graphene and colloidal semiconductor quantum dots (QDs/graphene) can combine the benefits of strong quantum confinement in the constituent components, such as high carrier mobility in graphene and large exciton binding energy in QDs, to enable extraordinary photoconductive gain and hence high photoresponse. Furthermore, QDs/graphene nanohybrids are inherently flexible, making them ideal for flexible photodetectors. Despite exciting progress made in rigid and flexible QDs/graphene photodetectors in broadband from UV to short-wave infrared, flexible middle-wave infrared (MWIR) photodetectors remain a challenge. Herein, we report the first success in fabrication of HgTe QDs/graphene nanohybrid ultrabroadband (400–4000 nm wavelength) photodetectors on flexible polyimide substrates via resolving critical issues of device fabrication on flexible substrates, which allowed flexible device performance approaching their counterparts on rigid substrates. Specifically, the flexible HgTe QDs/graphene nanohybrids photodetectors exhibited high responsivity (R*) across the ultrabroadband spectrum at room temperature. At 550 nm, 1.5 μm and 4.0 μm wavelengths, anR* of up to 0.65 AW⁻¹, 5.7 × 10⁻³AW⁻¹and 0.9 × 10⁻³AW⁻¹were achieved respectively. Bending tests confirmed performance stability of the flexible HgTe QDs/graphene nanohybrids photodetectors under repeated bending with up to 5.5 mm radius of curvature. Images taken in the ultrabroadband while the photodetectors in flat and bent states both show promising imaging quality. This result illustrates the potential applications of the uncooled, flexible HgTe QDs/graphene nanohybrids photodetectors in the ultrabroadband range of 400–4000 nm. 

Abstract Nanohybrids based on van der Waals (vdW) heterostructures of graphene (Gr) decorated with MoS₂nanodiscs (MoS₂-NDs) combine the advantages of high carrier mobility of graphene for high photoconductive gain and localized surface plasmonic resonance (LSPR) on MoS₂-NDs for enhanced light absorption. Considering MoS₂-NDs are obtained using dip-coating of (NH₄)₂MoS₄precursor followed with annealing in sulfur vapor at 450 °C, the annealing plays a critical role in controlling the MoS₂-NDs properties. This work investigated the effect of the annealing time on the MoS₂-NDs dimension and found the MoS₂-ND’s thickness was increased monotonically from bilayer to multilayer and diameter reduced from ∼900 nm to 600 nm with annealing time increased from 4 to 25 min. A similar increasing photoresponsivity observed on MoS₂-NDs/Gr with annealing time indicates the conversion of the (NH₄)₂MoS₄precursor to crystalline MoS₂initiated at the precursor/graphene interface and continued vertically. At the annealing time of ∼20 min, the MoS₂-NDs reached the optimal diameter (∼600 nm) and thickness (near or slightly above 4.2 nm) for LSPR while graphene remained unblemished, yielding the highest photoresponsivity up to 37 A W⁻¹(at 550 nm wavelength and 12 μW cm⁻²light intensity) on the MoS₂-NDs/Gr nanohybrids photodetectors which leads to enhanced detectivityD* by a factor of 320 over the quantum dots/graphene nanohybrid counterpart of comparable thickness and illustrates the benefits of LSPR induced in MoS₂-NDs for enhanced light absorption. 

Plasmonic metastructures have become valuable platforms for manipulating light based on polarization. While traditional approaches have focused on sorting light through front- or back-scattering, recent advances underscore the potential of in-plane light routing—guiding and separating photons across the surface of the metastructure itself. In this study, we investigate how lateral asymmetry in nanoantenna design—introduced along the direction of in-plane light propagation rather than the axis of illumination—can be leveraged for efficient polarization sorting. We focus on metasurfaces composed of arrays of both symmetric and asymmetric gold nanoantennas. Our results reveal that such structural asymmetry enables two distinct modes of operation: in one, photons with different polarizations are directed along separate in-plane paths; in the other, they follow the same axis but are emitted at different angles depending on their polarization. We further examine the spectral dependence of this sorting behavior and demonstrate that asymmetric metastructures can realize four-way polarization sorting, each with unique anisotropic characteristics. Our simulation results provide insight into how phase modulation of the scattered light—coupled into the substrate beneath the metasurface—is influenced by nanoantenna asymmetry. These findings pave the way for compact, on-chip implementations of the planar spin Hall effect and for simplified metasurfaces suited to sensing, optical switching, and beam steering applications. 

ABSTRACT Colloidal quantum dot/graphene (QD/Gr) nanohybrids rely on strong quantum confinement and offer a promising platform to design high‐performance quantum sensors such as photodetectors. In QD/Gr nanohybrid photodetectors, QDs absorb the incident light, and the spectral range is determined by the QD's semiconductor bandgap with moderate tunability by QD size, which presents a challenge for QDs/Gr nanohybrids to be used for detection of photons beyond such a conventional bandgap‐determined spectral range. In this work, we explored coupled self‐scintillation and X‐ray photodetection in PbS QD/Gr nanohybrids of sub‐micron active layer thickness for compromised X‐ray self‐scintillation by Pb of high X‐ray cross section and high‐gain detection enabled by graphene on both rigid and flexible substrates. An additional critical step found to suppress noise induced by interaction of polar molecules with dangling bonds on the QD surface was achieved by a poly(methyl methacrylate) capping layer, resulting in significantly improved signal‐to‐noise ratio. This allows a maximum X‐ray sensitivity of 280 C Gy⁻¹cm⁻², together with high responsivity in visible to infrared range on the order of 10 A/W. This result has demonstrated that the conventional bandgap‐determined spectral range can be significantly expanded through design of the QD/Gr nanohybrids. The demonstrated performance and mechanical flexibility provide a pathway toward durable, flexible quantum dot‐based detectors for multi‐spectrum sensing. 

Nanohybrids of graphene and colloidal semiconductor quantum dots (QDs/Gr) provide a promising quantum sensing scheme for photodetection. Despite exciting progress made in QDs/Gr photodetectors in broadband from ultraviolet to short-wave infrared, the device performance is limited in middle-wave infrared (MWIR) detection. A fundamental question arises as to whether the thermal noiseinduced dark current and hence poor signal-to-noise ratio in conventional uncooled MWIR photodetectors persist in QDs/ Gr nanohybrids. Herein, we investigated noise, responsivity (R*), and specific detectivity (D*) in HgTe QDs/Gr nanohybrids, revealing that the noise and R* are decoupled in nanohybrids and each can be optimized independently toward its theoretical limit. Specifically, the noise in the QDs/Gr nanohybrids is dominated by that of graphene with a negligible effect from the dark current in HgTe QDs and can be optimized to its intrinsic limit by removing charge doping of adsorbed polar molecules on graphene. Furthermore, the R* is proportional to the photoconductive gain enabled by the strong quantum confinement in QDs and Gr. Achieving high gain in the MWIR spectrum, however, is challenging and requires elimination of charge traps primarily from the surface states of the narrow-bandgap semiconductor HgTe QDs. Using grain-rotation-induced grain-coalescence growth of single-layer and core/shell HgTe QDs, we show the that HgTe QDs surface states caused by Te deficiency can be dramatically suppressed, resulting in high gain up to 4.0 × 107 in the MWIR spectrum. The optimized noise and R* have led to high uncooled MWIR D* up to 2.4 × 1011 Jones, making nanohybrids promising to surpass the fundamental dark-current limit in conventional photodetectors.