Colloidal quantum dots (QDs)/graphene nanohybrids provide a unique platform to design photodetectors of high performance. These photodetectors are quantum sensors due to the strong quantum confinement in QDs for spectral tunability, and in graphene for high charge mobility. Quantitatively, the high carrier mobility of graphene plays a critical role to enable high photoconductive gain and understanding its impact on the photodetector performance is imperative. Herein, we report a comparative study of PbS QDs/graphene nanohybrids with monolayer and bilayer graphene for broadband photodetection ranging from ultraviolet, visible, near-infrared to short-wave infrared spectra (wavelength: 400 nm–1750 nm) to determine if a specific advantage exists for one over the other. This study has revealed that both the monolayer and bilayer graphene grown in chemical vapor deposition can provide a highly efficient charge transfer channel for photo-generated carriers for high broadband photoresponse.
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Abstract Photodetectors based on colloidal quantum dots (QD)/graphene nanohybrids are quantum sensors due to strong quantum confinement in both QD and graphene. The optoelectronic properties of QD/graphene nanohybrids are affected by the quantum physics that predicts a high photoconductive gain and hence photoresponsivity (
R *) depending on the pixel length (L ) asR *∝L −2. Experimental confirmation of the effect of the pixel geometric parameters on the optoelectronic properties of the QD/graphene photodetector is therefore important to elucidate the underlying quantum physics. Motivated by this, an array of PbS QDs/graphene nanohybrid photodetectors are designed with variable QD/graphene pixel lengthL and width (W ) in the range of 10–150 µm for a study ofR* , noise, and specific detectivity (D *) in a broad spectrum of 400–1500 nm. Intriguingly,R* exhibits a monotonic decreasing trend of 1/L 2while being independent ofW , confirming experimentally the theoretical prediction. Interestingly, this geometric effect on the photoresponsivity seems to be partially compensated by that in noise, leading toD *independent ofL andW at wavelengths in the ultraviolet‐visible‐near infrared range. This result sheds light on the quantum physics underlying the optoelectronic process in QD/graphene nanohybrids, which is important to the design of high‐quality QD/graphene photodetectors and imaging systems.Free, publicly-accessible full text available May 1, 2025 -
Colloidal quantum dots/graphene (QD/Gr) nanohybrids have been studied intensively for photodetection in a broadband spectrum including ultraviolet, visible, near-infrared, and shortwave infrared (UV−vis-NIR-SWIR). Since the optoelectronic process in the QD/Gr nanohybrid relies on the photogenerated charge carrier transfer from QDs to graphene, understanding the role of the QD−QD and QD−Gr interfaces is imperative to the QD/Gr nanohybrid photodetection. Herein, a systematic study is carried out to probe the effect of these interfaces on the noise, photoresponse, and specific detectivity in the UV−vis-NIR-SWIR spectrum. Interestingly, the photoresponse has been found to be negligible without a 3-mercaptopropionic acid (MPA) ligand exchange, moderate with a single ligand exchange after all QD layers are deposited on graphene, and maximum if it is performed after each QD layer deposition up to five layers of total QD thickness of 260−280 nm. Furthermore, exposure of graphene to C-band UV (UVC) for a short period of 4−5 min before QD deposition leads to improved photoresponse via removal of polar molecules at the QD/Gr interface. With the combination of the MPA ligand exchange and UVC exposure, optimal optoelectronic properties can be obtained on the PbS QD/Gr nanohybrids with high specific detectivity up to 2.6 × 1011, 1.5 × 1011, 5 × 1010, and 1.9 × 109 Jones at 400, 550, 1000, and 1700 nm, respectively, making the nanohybrids promising for broadband photodetection.more » « lessFree, publicly-accessible full text available April 9, 2025
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Abstract Semiconductor quantum dots/graphene heterostructure nanohybrids combine the advantages of the enhanced light–matter interaction and spectral tunability of quantum dots (QDs) and high charge mobility in graphene as a charge transport pathway, providing a unique platform for exploration of photodetectors with high performance. In particular, the QDs/graphene nanohybrids allow resolution to the critical issue of charge transport in QDs-only photodetectors stemming from the low charge mobility associated with both QD surface defect states and inter-QD junctions. Furthermore, the achieved capability in industrial-scale fabrication of graphene and colloidal QDs has motivated efforts in research of QDs/graphene nanohybrids focal plane arrays that are expected to be not only high performance and low cost, but also light-weight, flexible and wearable. This paper aims to highlight recent progress made in the research and development of QDs/graphene nanohybrid photodetectors and discuss the challenges remained towards their commercial applications.more » « less
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Tong, Xin ; Wu, Jiang ; Wang, Zhiming (Ed.)Colloidal semiconductor quantum dot/graphene van der Waals heterostructure nanohybrids are emerging technologies for photodetection. These nanohybrids combine the advantages of the enhanced light-matter interaction and spectral tunability of quantum dots (QDs) and superior charge mobility in graphene, providing an affordable alternative for uncooled photodetectors with high gain or external quantum efficiency in a wide spectral range. In particular, the interfacing of QDs with high-mobility graphene as a charge transport pathway has provided an effective resolution to the critical issue of charge transport in QD-only photodetectors stemming from the low charge mobility associated with both QD surface defect states and QD-QD junctions. Furthermore, the achieved capability in industrial-scale fabrication of graphene, colloidal QDs, and QD/graphene nanohybrids has motivated efforts in researches of focal plane arrays that are expected to be not only high performance and low cost but also lightweight, flexible, and wearable. This chapter aims to provide an up-to-date review of the recent progress made in the research of QD/graphene nanohybrid photodetectors, together with a discussion on the challenges remaining and perspective in future research and development to make QD/graphene nanohybrids competitive for commercialization.more » « less
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Fulop, Gabor F. ; Kimata, Masafumi ; Zheng, Lucy ; Andresen, Bjørn F. ; Miller, John Lester (Ed.)Colloidal semiconductor quantum dots/graphene van der Waals (vdW) heterojunctions take advantages of the enhanced light-matter interaction and spectral tenability of quantum dots (QDs) and superior charge mobility in graphene, providing a promising alternative for uncooled infrared photodetectors with a gain or external quantum efficiency up to 1010. In these QD/graphene vdW heterostructures, the QD/graphene interface plays a critical role in controlling the optoelectronic process including exciton dissociation, charge injection and transport. Specifically, charge traps at the vdW interface can increase the noise, reduce the responsivity and response speed. This paper highlight our recent progress in engineering the vdW heterojunction interface towards more efficient charge transfer for higher photoresponsivity, D* and response speed. These results illustrate that the importance in vdW heterojunction interface engineering in QD/graphene photodetectors which may provide a promising pathway for low-cost, printable and flexible infrared detectors and imaging systems.more » « less
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Nanohybrids represent a larger variety of functional materials consisting of one or more types of low‐dimensional semiconductor nanostructures, such as quantum dots, nanowires, nanotubes, 2D atomic materials (graphene, transition‐metal dichalcogenides, etc.) interfaced with one another, and/or with conventional material matrices (bulks, films, polymers, etc.). Heterojunction interfaces are characteristic in nanohybrids and play a critical role facilitating synergistic coupling of constituent materials of different functionalities, resulting in excellent electronic, optoelectronic, and mechanical properties. Therefore, nanohybrids provide fresh opportunities for designs of optoelectronic devices of extraordinary performance in addition to the benefits of low cost, large abundance, flexibility, and light weight. Herein, some recent achievements in exploiting new optoelectronic nanohybrids and understanding the underlying physics toward high‐performance optoelectronic nanohybrids that are competitive in commercialization of various optoelectronic devices are highlighted. Using nanohybrid photodetectors as an example, the importance in controlling the heterojunction interfaces and multiscale controlling of optoelectronic process of light absorption, exciton dissociation, photocarrier transfer, and transport from atomic to device scales and how this control impacts the photodetector performance are revealed. The current status, remaining challenges, and future perspectives in optoelectronic nanohybrids are also discussed.