Light-emitting diodes (LEDs) based on excitonic material systems, in which tightly bound photoexcited electron–hole pairs migrate together rather than as individual charge carriers, offer an ...attractive route to developing solution-processed, high-performance light emitters. Here, we demonstrate bright, efficient, excitonic infrared LEDs through the incorporation of quantum dots (QDs)1 into a low-dimensional perovskite matrix. We program the surface of the QDs to trigger fast perovskite nucleation to achieve homogeneous incorporation of QDs into the matrix without detrimental QD aggregation, as verified by in situ grazing incidence wide-angle X-ray spectroscopy. We tailor the distribution of the perovskites to drive balanced ultrafast excitonic energy transfer to the QDs. The resulting LEDs operate in the short-wavelength infrared region, an important regime for imaging and sensing applications, and exhibit a high external quantum efficiency of 8.1% at 980 nm at a radiance of up to 7.4 W Sr−1 m−2.Embedding perovskite quantum dots in perovskite leads to bright, efficient 980 nm LEDs with applications in imaging and sensing.
All-printed transistors consisting of interconnected networks of various types of two-dimensional nanosheets are an important goal in nanoscience. Using electrolytic gating, we demonstrate ...all-printed, vertically stacked transistors with graphene source, drain, and gate electrodes, a transition metal dichalcogenide channel, and a boron nitride (BN) separator, all formed from nanosheet networks. The BN network contains an ionic liquid within its porous interior that allows electrolytic gating in a solid-like structure. Nanosheet network channels display on:off ratios of up to 600, transconductances exceeding 5 millisiemens, and mobilities of >0.1 square centimeters per volt per second. Unusually, the on-currents scaled with network thickness and volumetric capacitance. In contrast to other devices with comparable mobility, large capacitances, while hindering switching speeds, allow these devices to carry higher currents at relatively low drive voltages.
Surface passivation of the perovskite photo absorber is a key factor to improve the photovoltaic performance. So far robust passivation strategies have not yet been revealed. Here, we demonstrate a ...successful passivation strategy which controls the Fermi-level of the perovskite surface by improving the surface states. Such Fermi-level control caused band-bending between the surface and bulk of the perovskite, which enhanced the hole-extraction from the absorber bulk to the HTM side. As an added benefit, the inorganic passivation layer improved the device light stability. By depositing a thick protection layer on the complete device, a remarkable waterproofing effect was obtained. As a result, an enhancement of
V
OC
and the conversion efficiency from 20.5% to 22.1% was achieved. We revealed these passivation mechanisms and used perhydropoly(silazane) (PHPS) derived silica to control the perovskite surface states.
It could successfully control the band-bending of the perovskite semiconductor, which led to improvement of the photovoltaic performance.
Brain-inspired computing is a growing and interdisciplinary area of research that investigates how the computational principles of the biological brain can be translated into hardware design to ...achieve improved energy efficiency. Brain-inspired computing encompasses various subfields, including neuromorphic and in-memory computing, that have been shown to outperform traditional digital hardware in executing specific tasks. With the rising demand for more powerful yet energy-efficient hardware for large-scale
artificial neural networks
, brain-inspired computing is emerging as a promising solution for enabling energy-efficient computing and expanding AI to the edge. However, the vast scope of the field has made it challenging to compare and assess the effectiveness of the solutions compared to state-of-the-art digital counterparts. This systematic literature review provides a comprehensive overview of the latest advances in brain-inspired computing hardware. To ensure accessibility for researchers from diverse backgrounds, we begin by introducing key concepts and pointing out respective in-depth topical reviews. We continue with categorizing the dominant hardware platforms. We highlight various studies and potential applications that could greatly benefit from brain-inspired computing systems and compare their reported computational accuracy. Finally, to have a fair comparison of the performance of different approaches, we employ a standardized normalization approach for energy efficiency reports in the literature.
Graphical abstract
Unconventional computing, including its four major, partly overlapping, brain-inspired computating frameworks: In-memory, neuromorphic, reservoir, and hyperdimensional computing
ZnS–CuInS2 (ZCIS) alloy nanostructures are becoming increasingly important materials because of their photoluminescence properties. Here we explore the emission properties of ZCIS quantum dots (QDs) ...capped with dodecanethiol, which exhibit Zn:Cu-dependent emission properties. Absorption and photoluminescence excitation spectra indicate a single, composition-independent light absorbing state. The emission spectra point out the existence of two emissive states with lifetimes of ∼10 ns and ∼100 ns. The photoluminescence and time-resolved emission analysis provide insight into the synergy between the two intraband states and the possibility of modulating the emission through variation in the Zn/Cu ratio. Better understanding of light absorbing and emission mechanisms in alloyed nanostructures is essential for future development of photoelectric and display devices.
Nanoparticles are the focus of much attention due to their astonishing properties and numerous possibilities for applications in nanotechnology. For realising versatile functions, assembly of ...nanoparticles in regular patterns on surfaces and at interfaces is required. Assembling nanoparticles generates new nanostructures, which have unforeseen collective, intrinsic physical properties. These properties can be exploited for multipurpose applications in nanoelectronics, spintronics, sensors, etc. This review surveys different techniques, currently employed and being developed, for assembling nanoparticles in to ordered nanostructures. In this endeavour, the principles and methods involved in the development of assemblies are discussed. Subsequently, different possibilities of nanoparticle-based nanostructures, obtained in multi-dimensions, are presented.
Multinary semiconductor nanoparticles such as CuInS2, AgInS2, and the corresponding alloys with ZnS hold promise for designing future quantum dot light-emitting devices (QLED). The QLED architectures ...require matching of energy levels between the different electron and hole transport layers. In addition to energy level alignment, conductivity and charge transfer interactions within these layers determine the overall efficiency of QLED. By employing CuInS2–ZnS QDs we succeeded in fabricating red-emitting QLED using two different hole-transporting materials, polyvinylcarbazole and poly(4-butylphenyldiphenylamine). Despite the similarity of the HOMO–LUMO energy levels of these two hole transport materials, the QLED devices exhibit distinctly different voltage dependence. The difference in onset voltage and excited state interactions shows the complexity involved in selecting the hole transport materials for display devices.
Photoinduced electron transfer processes from semiconductor quantum dots (QDs) molecularly bridged to a mesoporous oxide phase are quantitatively surveyed using optical pump–terahertz probe ...spectroscopy. We control electron transfer rates in donor–bridge–acceptor systems by tuning the electronic coupling strength through the use of n-methylene (SH–CH2 n –COOH) and n-phenylene (SH–C6H4 n –COOH) molecular bridges. Our results show that electron transfer occurs as a nonresonant quantum tunneling process with characteristic decay rates of β n = 0.94 ± 0.08 and β n = 1.25 per methylene and phenylene group, respectively, in quantitative agreement with reported conductance measurements through single molecules and self-assembled monolayers. For a given QD donor–oxide acceptor separation distance, the aromatic n-phenylene based bridges allow faster electron transfer processes when compared with n-methylene based ones. Implications of these results for QD sensitized solar cell design are discussed.
Thermalization losses limit the photon-to-power conversion of solar cells at the high-energy side of the solar spectrum, as electrons quickly lose their energy relaxing to the band edge. Hot-electron ...transfer could reduce these losses. Here, we demonstrate fast and efficient hot-electron transfer between lead selenide and cadmium selenide quantum dots assembled in a quantum-dot heterojunction solid. In this system, the energy structure of the absorber material and of the electron extracting material can be easily tuned via a variation of quantum-dot size, allowing us to tailor the energetics of the transfer process for device applications. The efficiency of the transfer process increases with excitation energy as a result of the more favorable competition between hot-electron transfer and electron cooling. The experimental picture is supported by time-domain density functional theory calculations, showing that electron density is transferred from lead selenide to cadmium selenide quantum dots on the sub-picosecond timescale.
Solution-processable two-dimensional (2D) semiconductors with chemically tunable thickness and associated tunable band gaps are highly promising materials for ultrathin optoelectronics. Here, the ...properties of free charge carriers and excitons in 2D PbS nanosheets of different thickness are investigated by means of optical pump-terahertz probe spectroscopy. By analyzing the frequency-dependent THz response, a large quantum yield of excitons is found. The scattering time of free charge carriers increases with nanosheet thickness, which is ascribed to reduced effects of surface defects and ligands in thicker nanosheets. The data discussed provide values for the DC mobility in the range 550-1000 cm
2
V
−1
s
−1
for PbS nanosheets with thicknesses ranging from 4 to 16 nm. Results underpin the suitability of colloidal 2D PbS nanosheets for optoelectronic applications.
Colloidal two-dimensional (2D) PbS nanosheets exhibit stable excitons and highly mobile charge carriers (500-1000 cm
2
V
−1
s
−1
) rendering solution-processed nanomaterials suitable for ultrathin optoelectronics.
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