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Zinc oxide nanoparticles (ZnO NPs) have been actively pursued as the most effective electron transport layer for quantum-dot light-emitting diodes (QLEDs) in light of their unique optical and electronic properties and low-temperature processing. However, the high electron mobility and smooth energy level alignment at QDs/ZnO/cathode interfaces cause electron over-injection, which aggravates non-radiative Auger recombination. Meanwhile, the abundant defects hydroxyl group (-OH) and oxygen vacancies (O V ) in ZnO NPs act as trap states inducing exciton quenching, which synergistically reduces the effective radiation recombination for degrading the device performance. Here, we develop a bifunctional surface engineering strategy to synthesize ZnO NPs with low defect density and high environmental stability by using ethylenediaminetetraacetic acid dipotassium salt (EDTAK) as an additive. The additive effectively passivates surface defects in ZnO NPs and induces chemical doping simultaneously. Bifunctional engineering alleviates electron excess injection by elevating the conduction band level of ZnO to promote charge balance. As a result, state-of-the-art blue QLEDs with an EQE of 16.31% and a T 50 @100 cd m -2 of 1685 h are achieved, providing a novel and effective strategy to fabricate blue QLEDs with high efficiency and a long operating lifetime.

A series of glycan-coated quantum dots were prepared to probe the effect of glycan presentation in intracellular localization in HeLa and SV40 epithelial cells. We show that glycan density mostly impacts on cell toxicity, whereas glycan type affects the cell uptake and intracellular localization. Moreover, we show that lactose can act as a "Trojan horse" on bi-functionalized QDs to help intracellular delivery of other non-internalizable glycan moieties and largely avoid the endosomal/lysosomal degradative pathway., (Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The rapid development of optoelectronic devices with biomimetic synaptic behavior holds significant potential for neuromorphic visual applications. However, considerable challenges remain including convenient device fabrication and low toxicity materials innovation. Here, a heterojunction phototransistor is constructed using low‐toxic CuZnInSSe (CIZS) colloidal quantum dots and amorphous InGaZnO (IGZO), which demonstrates high specific detectivity of 3.4 × 1015 Jones in visible light spectrum. Moreover, it is found that the photoresponse speed can be controlled via a ligand exchange treatment, through that the response speed can be adjusted from 0.3 to 11 s. This enables the device to operate in two distinct modes: a typical fast sensing mode and a neuromorphic visual mode. In the neuromorphic visual mode, the device's synaptic behavior can be tuned by manipulating light pulse intensity, frequency, wavelength, and gate voltage. As a demonstration, a phototransistor array effectively implements image pre‐processing functions, including color recognition, visual memorizing, and forgetting. [ABSTRACT FROM AUTHOR]

Flexible direct X‐ray detectors based on perovskites have great potential for X‐ray imaging due to their high sensitivity, low detection limit, low‐cost, and large‐area fabrication. However, these detectors perform inefficiently at X‐ray‐to‐current conversion because of inadequate functional layer thickness and charge‐carrier recombination. Here, the fabrication of an integrated, self‐powered X‐ray detector based on CsPbBr3 quantum dots and a MAPbI3 photoelectric conversion layer embedded with perylene diimide molecules is reported. In addition to optimizing crystal domain formation and charge carrier extraction, the perylene diimide molecules also improve the electron mobility of MAPbI3 films by twofold. The integrated perovskite‐based X‐ray detector has a sensitivity of 143 169 ± 848 µC Gyair−1 cm−2 and a detection limit of 30.77 nGy s−1. The perylene diimide molecule at the grain boundary of MAPbI3 shows defect passivation and charge collection characteristics, leading to stable output over 30 bending cycles. This hybrid molecular approach provides insight into a general method to modify device performance using perylene diimide‐integrated detectors for X‐ray imaging of 3D objects with curved surfaces. [ABSTRACT FROM AUTHOR]

Emerging Pb‐based photovoltaic (PV) technologies, including in particular solution processed halide perovskite solar cells (PSCs) and Pb chalcogenide quantum dot solar cells (QDSCs), are among the most promising next‐generation PV technologies for a range of disruptive energy and electronic applications. However, the potential toxicity and leakage of hazardous Pb species have become one of the main barriers to their large‐scale application. When solar cells are subject to physical damage or failure of encapsulation, rapid leakage of Pb may occur, which can be accelerated by exposure to external environmental weathering conditions such as rainfall and elevated temperature. Herein, an in‐depth investigation on the essential role of Pb in PSCs and QDSCs, as well as common causes of Pb leakage, is undertaken. The hazardous effects of Pb toxicity on soil plants, bacteria, animals, and human cells are also evaluated. Recent progress in developing effective strategies for Pb leakage reduction, such as Pb‐free or Pb‐less perovskite materials, device architecture design, encapsulation absorbers for PSCs, and core–shell structure and ligand exchange method for QDSCs, in addition to Pb recycling strategies of end‐of‐life solar cells are summarized. This review provides quantitative insights into the future development of eco‐friendly emerging Pb‐based PV technologies. [ABSTRACT FROM AUTHOR]

Lead halide perovskite solar cells (PSCs) have emerged as a highly promising next‐generation photovoltaic (PV) technology that combines high device performance with ease of processing and low cost. However, the potential leaching of lead is recognized as a major environmental concern for their large‐scale commercialization, especially for application areas with significant overlap with human life. Herein, a quantitative kinetic analysis of the Pb leaching behavior of five types of benchmark PSCs, namely, MAPbI3, FA0.95MA0.05Pb(I0.95Br0.05)3, Cs0.05(FA0.85MA0.15)0.95Pb(I0.85Br0.15)3, CsPbI3, and CsPbI2Br, under laboratory rainfall conditions is reported. Strikingly, over 60% of the Pb contained in the unencapsulated perovskite devices is leached within the first 120 s under rainfall exposure, suggesting that very rapid leaching of Pb can occur when indoor and outdoor PV devices are subject to physical damage or failed encapsulation. The initial Pb leaching rate is found to be strongly dependent on the types of PSCs, pointing to a potential route toward Pb leaching reduction through further optimization of their materials design. The findings offer kinetic insights into the Pb leaching behavior of PSCs upon aqueous exposure, highlighting the urgency to develop robust mitigation methods to avoid a potentially catastrophic impact on the environment for their large‐scale deployment. [ABSTRACT FROM AUTHOR]

White light emission is of great importance in our daily life as it is the primary source of light indoor and outdoor as well as day and night. Among various materials and lighting technologies, intensive efforts have been made to quantum dots based‐light‐emitting diode (QD‐LEDs, or QLEDs) because of outstanding optical properties, facile synthesis, and bandgap tunability of QDs. Despite the fact that QLEDs are able to present various colors in a visible range, realizing efficient direct white light emission is a challenge as white light emission can only be achievable through stacking and patterning of QD films or mixing of different sizes of QDs. This inevitably involves energy band mismatch at interfaces, leading to degradation of device performance. Here, a new effective method to improve white QLED performances through embedding a ferroelectric islands structure is introduced, which induces an electric field to effectively modulate the energy band at the junction interface. The formation of a favorable energy landscape leads to efficient charge transport, improved radiative recombination, and consequently high external quantum efficiency in the white QLEDs. In addition, it is demonstrated that this new approach is proved to be effective in different color temperatures ranging from 3000 to over 120 000 K. [ABSTRACT FROM AUTHOR]

Colloidal quantum dots (QDs) have unique optical and electrical properties with promising applications in next‐generation semiconductor technologies, including displays, lighting, solar cells, photodetectors, and image sensors. Advanced analytical tools to probe the optical, morphological, structural, compositional, and electrical properties of QDs and their ensemble solid films are of paramount importance for the understanding of their device performance. In this review, comprehensive studies on the state‐of‐the‐art metrology approaches used in QD research are introduced, with particular focus on time‐resolved (TR) and spatially resolved (SR) spectroscopy and microscopy. Through discussing these analysis techniques in different QD system, such as various compositions, sizes, and shell structures, the critical roles of these TR‐spectroscopic and SR‐microscopic techniques are highlighted, which provide the structural, morphological, compositional, optical, and electrical information to precisely design QDs and QD solid films. The employment of TR and SR analysis in integrated QD device systems is also discussed, which can offer detailed microstructural information for achieving high performance in specific applications. In the end, the current limitations of these analytical tools are discussed, and the future development of the possibility of interdisciplinary research in both QD fundamental and applied fields is prospected. [ABSTRACT FROM AUTHOR]

Colloidal metal chalcogenide quantum dots (QDs) have excellent quantum efficiency in light–matter interactions and good device stability. However, QDs have been brought to the forefront as viable building blocks in bottom‐up assembling semiconductor devices, the development of QD solar cell (QDSC) is still confronting considerable challenges compared to other QD technologies due to their low performance under natural sunlight, as a consequence of untapped potential from their quantized density‐of‐state and inorganic natures. This report is designed to address this long‐standing challenge by accessing the feasibility of using QDSC for indoor and concentration PV (CPV) applications. This work finds that above bandgap photon energy irradiation of QD solids can generate high densities of excitons via multi‐photon absorption (MPA), and these excitons are not limited to diffuse by Auger recombination up to 1.5 × 1019 cm−3 densities. Based on these findings, a 19.5% (2000 lux indoor light) and an 11.6% efficiency (1.5 Suns) have been facilely realized from ordinary QDSCs (9.55% under 1 Sun). To further illustrate the potential of the MPA in QDSCs, 21.29% efficiency polymer lens CPVs (4.08 Suns) and viable sensor networks powered by indoor QDSCs matrix have been demonstrated. [ABSTRACT FROM AUTHOR]

To improve quantum dot solar cell performance, it is crucial to make efficient use of the available incident sunlight to ensure that the absorption is maximized. The ability of metal nanoparticles to concentrate incident sunlight via plasmon resonance can enhance the overall absorption of photovoltaic cells due to the strong confinement that results from near-field coupling or far-field scattering plasmonic effects. Therefore, to simultaneously and synergistically utilize both plasmonic effects, the placement of different plasmonic nanostructures at the appropriate locations in the device structure is also critical. Here, we introduce two different plasmonic nanoparticles, Au and Ag, to a colloidal PbS quantum dot heterojunction at the top and bottom interface of the electrodes for further improvement of the absorption in the visible and near-infrared spectral regions. The Ag nanoparticles exhibit strong scattering whereas the Au nanoparticles exhibit an intense optical effect in the wavelength region where the absorption of light of the PbS quantum dot is strongest. It is found that these dual-plasmon layers provide significantly improved short-circuit current and power conversion efficiency without any form of trade-off in terms of the fill factor and open-circuit voltage, which may result from the indirect contact between the plasmonic nanoparticles and colloidal quantum dot films. [ABSTRACT FROM AUTHOR]

The development of flexible displays for wearable electronics applications has created demand for high‐performance quantum dot (QD) light‐emitting diodes (QLEDs) based on QD core@shell structures. Emerging indium phosphide (InP)‐based core@shell QDs show promise as lighting material in the field of optoelectronics because they are environmentally friendly material, can be produced in a cost‐effective manner, and are capable of tunable emission. While efforts have been made to enhance the performance of InP‐based QLED, the stabilities of InP@ZnSeS QDs film and InP@ZnSeS‐based QLED in water/air are not yet fully understood, limiting their practical applications. Herein, a highly durable, flexible InP@ZnSeS QLED encapsulated in an ultrathin film of CYTOP, a solution‐based amorphous fluoropolymer, is demonstrated. The CYTOP‐encapsulated green flexible QLED shows an external quantum efficiency (EQE) of 0.904% and a high luminescence of 1593 cd m−2 as well as outstanding waterproof performance. The flexible device emits strong luminescence after being immersed in water for ≈20 min. Even when subjected to continuous tensile stress with a 5 mm bending radius, the high luminescence is preserved. This waterproof architecture can be a promising strategy for wearable electronics applications. [ABSTRACT FROM AUTHOR]

Energy harvesting, which converts wasted environmental energy into electricity by utilizing various physical effects, hasattracted tremendous research interests as is one of the key technologies to realize advanced electronics in the future. In this review, we introduce recent progress in the field of hybrid energy harvesting technology. In particular, we focus on a quantum dots (QD)‐based hybrid energy harvesting device. Attributed to fascinating material properties that QD possess, employment of QDs into hybrid energy harvesting has shown great potential for independent and sustainable energy supply.First, an integration of a QD solar cell into a mechanical energy harvester is discussed to harness different types of environmental energy sources simultaneously. Second, a comprehensive explanation of a piezotronic and piezo‐phototronic effect is provided, which is followed by QD‐based piezo‐phototronic applications. Finally, we summarize recent progress that has been made in energy harvesting technology involving a photovoltaic and piezo/triboelectric effect [ABSTRACT FROM AUTHOR]

Photocatalytic production of hydrogen from water can directly convert solar energy into chemical energy storage, which has significant advantages and great promise. As an emerging photosensitizer, the efficiency of quantum dots (QDs) based artificial photosynthetic system have made breakthroughs. In this review, we will give a summary of the development of QDs based photocatalytic hydrogen evolution in these years. First, we highlight different types of hydrogen evolution catalyst combined with QDs; then we focus on the surface modification and heterostructure formation of QDs to improve the photocatalytic efficiency, respectively. In the end, we will propose some Cd‐free QDs and future development of photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Anisotropic nanowires are promising candidates for electronic thermal management due to their unique electrical and thermal properties. However, eco-friendly solution-processed nanomaterials with an elaborate morphology and microstructure for modulating thermal and charge transfer are still a considerable challenge. Herein, we present a simple but effective approach for synthesizing pseudo core-shell nanowires through quantum dot (QD)-like nanostructure coating (p-NW@QD) to generate exceptional electron-phonon transport properties. With the assistance of diphenyl ether as a coordination solvent, high crystallinity lead sulfide NWs can be fabricated with a large aspect ratio together with uniform QD coating. This p-NW@QD exhibits high electronic mobility (30.65 cm2/Vs) as well as a diameter independent low thermal conductivity (1.53 ± 1 W/m K). Direct charge/heat carrier flow measurements and computational simulations demonstrate that the unusual electrical and thermal transport phenomenon is strongly dependent on the fast charge transport through the QD shell, and a slow phonon migration across the Umklapp process dominated NW cores. These findings indicate a significant step toward colloidal synthesis nanostructures for future high-performance nanoelectronics and thermal energy devices. [ABSTRACT FROM AUTHOR]

Abstract: Colloidal quantum dots are promising materials for flexible solar cells, as they have a large absorption coefficient at visible and infrared wavelengths, a band gap that can be tuned across the solar spectrum, and compatibility with solution processing. However, the performance of flexible solar cells can be degraded by the loss of charge carriers due to recombination pathways that exist at a junction interface as well as the strained interface of the semiconducting layers. The modulation of the charge carrier transport by the piezoelectric effect is an effective way of resolving and improving the inherent material and structural defects. By inserting a porous piezoelectric poly(vinylidenefluoride‐trifluoroethylene) layer so as to generate a converging electric field, it is possible to modulate the junction properties and consequently enhance the charge carrier behavior at the junction. This study shows that due to a reduction in the recombination and an improvement in the carrier extraction, a 38% increase in the current density along with a concomitant increase of 37% in the power conversion efficiency of flexible quantum dots solar cells can be achieved by modulating the junction properties using the piezoelectric effect. [ABSTRACT FROM AUTHOR]

A series of glycan-coated quantum dots were prepared to probe the effect of glycan presentation in intracellular localization in HeLa and SV40 epithelial cells. We show that glycan density mostly impacts on cell toxicity, whereas glycan type affects the cell uptake and intracellular localization. Moreover, we show that lactose can act as a 'Trojan horse' on bi-functionalized QDs to help intracellular delivery of other non-internalizable glycan moieties and largely avoid the endosomal/lysosomal degradative pathway. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of soft templates in the synthesis of ZnSe nanocrystals realized through a surfactant/cosurfactant system was investigated and a micelle formation process model was proposed. Through freeze-fracture electron microscopy, it was proven that template micelles were formed in the zinc precursors. Furthermore, it was found that a long stirring period was essential for achieving the lowest energy state of the soft templates which were used for synthesizing monodisperse ZnSe quantum dots. [Copyright &y& Elsevier]

[Display omitted] • A unique nanotree-like quaternary superstructure is successfully prepared. • This multi-dimensional composite enhances solar absorption and carrier separation. • The unique quaternary composite realizes the high-performance PCP application. • Time-delay protection also could be realized due to the unique nanotree structure. • The PCP mechanism is clarified by DFT calculation. Stainless steels typically feature high toughness and good corrosion resistance. However, pitting corrosion can easily occur on stainless steel and the passivation film tends to be vulnerable under pressure or in brine environments. Metal corrosion is a long-standing challenge for the steel industry, forging a path to net-zero. Herein, by successive growth of a series of quantum confined nanocrystals such as quantum dots and nanorods with gradient band energy level alignment, high-performance photoelectrochemical cathodic protection for steel is demonstrated with remarkable mechanical and electrochemical stability. Under simulated solar light illumination, effective photoinduced protection can be realized for 304 stainless steel which enables long-term corrosion resistance in a 3.5 wt% NaCl solution. Unique nanotree-like structures and the quaternary material combination can store excess charges and release them gradually, enabling time-delay protection for metals after light excitation. Various promising functionalities as unique photoelectrodes can be envisioned arising from the proposed 3D nanotree morphology. [ABSTRACT FROM AUTHOR]