Lead sulfide (PbS) colloidal quantum dots (QDs) have received attentions as materials for near-infrared (NIR) photodetection in view of their strong and tunable absorption in the NIR region and room-temperature solution processability. However, the realization of high-speed PbS QD photodetection has been severely hindered by the extremely low carrier mobility (∼10 −5 to 10 −2 cm 2 V −1 s −1 ). Here, an ultrafast PbS QD photodiode fabricated with low mobility QDs (∼10 −3 cm 2 V −1 s −1 ) is demonstrated, which has rise/fall times as short as 0.33 μs at zero voltage bias. The fast response is achieved by engineering resistor−capacitor (RC) time delay and charge transport in the device. The photodiode also has an external quantum efficiency (EQE) exceeding 100% under voltage bias, which is possibly due to the photoconductive gain induced by hole transport layer (HTL). The photoconductive gain combined with low noise current enables high sensitivity with a specific detectivity value up to 3.2 × 10 11 Jones at 1125 nm.

Control over the anisotropic assembly of small building blocks into organized structures is considered an effective way to design organic nanosheets and atomically thick inorganic nanosheets with nonlayered structure. However, there is still no available route so far to control the assembly of inorganic and organic building blocks into a flattened hybrid nanosheet with atomic thickness. Herein, we highlight for the first time a universal in-plane coassembly process for the design and synthesis of transition-metal chalcogenide-alkylamine inorganic-organic hybrid nanosheets with atomic thickness. The structure, formation mechanism, and stability of the hybrid nanosheets were investigated in detail by taking the Co₉S₈-oleylamine (Co₉S₈-OA) hybrid nanosheets as an example. Both experimental data and theoretical simulations demonstrate that the hybrid nanosheets were formed by in-plane connection of small two-dimensional (2D) Co₉S₈ nanoplates via oleylamine molecules adsorbed at the side surface and corner sites of the nanoplates. X-ray absorption fine structure spectroscopy study reveals the structure distortion of the small 2D Co₉S₈ nanoplates that endows structural stability of the atomically thick Co₉S₈-OA hybrid nanosheets. The brand new atomically thick nanosheets with inorganic-organic hybrid network nanostructure will not only enrich the family of atomically thick 2D nanosheets but also inspire more interest in their potential applications.

Sensitizing crystalline silicon (c-Si) with an infrared-sensitive material, such as lead sulfide (PbS) colloidal quantum dots (CQDs), provides a straightforward strategy for enhancing the infrared-light sensitivity of a Si-based photodetector. However, it remains challenging to construct a high-efficiency photodetector based upon a Si:CQD heterojunction. Herein, we demonstrate that Si surface passivation is crucial for building a high-performance Si:CQD heterojunction photodetector. We have studied one-step methyl iodine (CH 3 I) and two-step chlorination/methylation processes for Si surface passivation. Transient photocurrent (TPC) and transient photovoltage (TPV) decay measurements reveal that the two-step passivated Si:CQD interface exhibits fewer trap states and decreased recombination rates. These passivated substrates were incorporated into prototype Si:CQD infrared photodiodes, and the best performance photodiode based upon the two-step passivation shows an external quantum efficiency (EQE) of 31% at 1280 nm, which represents a near 2-fold increase over the standard device based upon the one-step CH 3 I passivated Si.

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A stretchable transmissive hexagonal diffraction grating, which has the potential to act as an optical diffuser, is demonstrated. Leveraging the simplicity of the self‐assembly fabrication process, the photon manipulation capability of polystyrene nanosphere arrays, and elastomeric properties of polydimethylsiloxane, the proposed device is capable of reproducible in situ tuning of both diffraction efficiency and spectral range. While being able to achieve maximum diffraction efficiencies of about 80%, the device displays highly efficient and broadband light diffusion fairly independent of incident light polarization and angle of incidence. Due to its efficient and tunable diffraction capabilities, one potential application of the reported device can be broadband photon management in solar cells and photodetectors by significant increase of the light path length inside the light‐absorbing thin films of these devices. As a proof of concept, the proposed optical diffuser is utilized for light absorption enhancement in colloidal quantum dot semiconductor thin films. The demonstrated devices enable integration of cheap and widely used materials with simple cost‐effective fabrication for photon management in optics, photonics, and optoelectronics.

Printed electronics fill the niches for low-cost, flexible devices in electronics. Developing substrates suitable for various printable electronic inks becomes an important topic in both academia and industry. Because of their extraordinary properties like solution processability, colloidal quantum dots (QDs) are gradually emerging in this field as promising candidates for electronic inks. In recent years, researchers have successfully produced high quality PbS QD inks in polar solvents. However, the incorporation of electronic inks onto a well-passivated substrate remains challenging due to the processing incompatibility between polar solvents and hydrophobic substrates. Here, we propose a surface modification strategy by using chlorine to achieve both trap-site suppression and a hydrophilic surface. The chlorine can effectively passivate the surface dangling bonds and charged hydroxyls while creating a hydrophilic surface. On this modified substrate, the contact angle between the water droplet and the SiO 2 substrate can be as small as 20° and this strategy is also feasible for other polymer and inorganic substrates. For a proof-of-concept demonstration, we fabricated a PbS QD ink-based field-effect transistor on a Cl-passivated substrate, and the device showed a mobility as high as 4.36 × 10 –3 cm 2 /V s, which indicates effective trap-site suppression. This device also enables the potential of the Cl-passivated substrates for QD inks with water or other polar solvents.

We report the use of an ecofriendly and recyclable CNC material as the host matrix for luminescent solar concentrator applications.

We report the patterning of metal electrodes on water-soluble nanofibril papers using PDMS stencil lithography. Strain sensors fabricated with silver nanoparticles on patterned metal electrodes show high gauge-factors of over 50 in strain testing.