Graphene

Inkjet Printing Multicolor Pixelated Quantum Dots on Graphene for Broadband Photodetection

“…Considering the photoconductive gain is proportional to the ratio of the two time constants τ exciton /τ transit that can be as high as 10 8 in QD/graphene devices, EQE ≫ 100% can be obtained. This means that the effective charges detected in the graphene layer can exceed one charge per photon. , The performance of the PbS-QDs/graphene device is comparable to the previous report of ∼8.4 A/W with similar graphene channel dimensions . However, the ZnO-QDs/graphene channel has significantly improved performance than previously reported (∼0.5 A/W) .…”

“…Finally, the ZnO-QDs/graphene channel has a photoresponsivity of 97.5 A/W (24.4 A/W·V) at a wavelength of 340 nm and a power of 6.66 μW and with an external quantum efficiency (EQE) value of 35580%. The large EQE in exceeding 100% can be attributed to photoconductive gain in the QDs/graphene photoconductive photodetectors. , In these devices, large photoconductive gains up to 10 8 have been demonstrated due to the combination of the strong quantum confinement in QDs and high charge mobility in graphene. , The former leads to long lifetime (τ exciton ) of excitons or electron–hole pairs and hence the trapped charges (after the transfer of the other type of charges to graphene) in the QDs. The latter facilitates short transit time of charges (τ transit ) between the source an drain electrodes.…”

Graphene/WS2 Nanodisk Van der Waals Heterostructures on Plasmonic Ag Nanoparticle-Embedded Silica Metafilms for High-Performance Photodetectors

“…The detectivity ( D *) can be defined as where A is the active area of the photodetector, NEP is the noise equivalent power, and i n 2 is the noise current. With the assumption that the noise limiting the detectivity is dominated by shot noise from the dark current I dark in the graphene channel, the detectivity can be expressed as . The maximum EQEs and D * of 2390% and 4.3 × 10 10 Jones are found at the wavelength of 450 nm.…”

Probing performance limiting factors in uncooled quantum dots/graphene SWIR-MWIR detectors

“…1,2 The missing or weak inter-plane interaction implies the strong quantum confinement of charge carriers in the 2D plane, resulting in superior physical properties including high charge carrier mobility, optical transparency, flexibility and chemical stability. 1,2 Since large-size, monolayer graphene can be fabricated using chemical vapor deposition (CVD), it could be viewed as thin film of atomically small thickness of 0.34 nm 3,4 and is compatible with the established microfabrication processes for making graphene-based microelectronic circuits. This is important to graphene-based applications involving graphene only and graphene nanohybrids consisting of graphene and nanostructures of other materials.…”

“…Even considering 100% external quantum efficiency (EQE) the responsivity would be less than 20 mA/W. 9 In order to increase the photoresponsivity, optoelectronic nanohybrids consisting of graphene and semiconductor nanostructures with the appropriate bandgaps or optical cutoffs have been investigated extensively. Among others, the one based on graphene and colloidal quantum dots heterostructures (QD/Gr) are particularly promising for photodetectors, 10 taking advantages of recent research progress in development of colloidal QDs of semiconductors of different bandgaps and hence different optical cutoffs for photodetection in different spectral range [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] and high carrier mobility graphene for high-performance photodetection.…”