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1.
Nanoscale systems are forecast to be a means of integrating desirable attributes of molecular and bulk regimes into easily processed materials. Notable examples include plastic light-emitting devices and organic solar cells, the operation of which hinge on the formation of electronic excited states, excitons, in complex nanostructured materials. The spectroscopy of nanoscale materials reveals details of their collective excited states, characterized by atoms or molecules working together to capture and redistribute excitation. What is special about excitons in nanometre-sized materials? Here we present a cross-disciplinary review of the essential characteristics of excitons in nanoscience. Topics covered include confinement effects, localization versus delocalization, exciton binding energy, exchange interactions and exciton fine structure, exciton-vibration coupling and dynamics of excitons. Important examples are presented in a commentary that overviews the present understanding of excitons in quantum dots, conjugated polymers, carbon nanotubes and photosynthetic light-harvesting antenna complexes.  相似文献   

2.
Organic photovoltaics are an important part of a next‐generation energy‐harvesting technology that uses a practically infinite pollutant‐free energy source. They have the advantages of light weight, solution processability, cheap materials, low production cost, and deformability. However, to date, the moderate photovoltaic efficiencies and poor stabilities of organic photovoltaics impede their use as replacements for inorganic photovoltaics. Recent developments in bulk‐heterojunction organic photovoltaics mean that they have almost reached the lower efficiency limit for feasible commercialization. In this review article, the recent understanding of the ideal bulk‐heterojunction morphology of the photoactive layer for efficient exciton dissociation and charge transport is described, and recent attempts as well as early‐stage trials to realize this ideal morphology are discussed systematically from a morphological viewpoint. The various approaches to optimizing morphologies consisting of an interpenetrating bicontinuous network with appropriate domain sizes and mixed regions are categorized, and in each category, the recent trends in the morphology control on the multilength scale are highlighted and discussed in detail. This review article concludes by identifying the remaining challenges for the control of active layer morphologies and by providing perspectives toward real application and commercialization of organic photovoltaics.  相似文献   

3.
Conjugated multi‐chromophore organic nanostructured materials have recently emerged as a new class of functional materials for developing efficient light‐harvesting, photosensitization, photocatalysis, and sensor devices because of their unique photophysical and photochemical properties. Here, we demonstrate the formation of various nanostructures (fibers and flakes) related to the molecular arrangement (H‐aggregation) of quaterthiophene (QTH) molecules and their influence on the photophysical properties. XRD studies confirm that the fiber structure consists of >95% crystalline material, whereas the flake structure is almost completely amorphous and the microstrain in flake‐shaped QTH is significantly higher than that of QTH in solution. The influence of the aggregation of the QTH molecules on their photoswitching and thermoresponsive photoluminescence properties is revealed. Time‐resolved anisotropic studies further unveil the relaxation dynamics and restricted chromophore properties of the self‐assembled nano/microstructured morphologies. Further investigations should pave the way for the future development of organic electronics, photovoltaics, and light‐harvesting systems based on π‐conjugated multi‐chromophore organic nanostructured materials.  相似文献   

4.
Solution processable semiconductors like organics and emerging lead halide perovskites (LHPs) are ideal candidates for photovoltaics combining high performance and flexibility with reduced manufacturing cost. Moreover, the study of hybrid semiconductors would lead to advanced structures and deep understanding that will propel this field even further. Herein, a novel device architecture involving block copolymer/perovskite hybrid bulk heterointerfaces is investigated, such a modification could enhance light absorption, create an energy level cascade, and provides a thin hydrophobic layer, thus enabling enhanced carrier generation, promoting energy transfer and preventing moisture invasion, respectively. The resulting hybrid block copolymer/perovskite solar cell exhibits a champion efficiency of 24.07% for 0.0725 cm2-sized devices and 21.44% for 1 cm2-sized devices, respectively, together with enhanced stability, which is among the highest reports of organic/perovskite hybrid devices. More importantly, this approach has been effectively extended to other LHPs with different chemical compositions like MAPbI3 and CsPbI3, which may shed light on the design of highly efficient block copolymer/perovskite hybrid materials and architectures that would overcome current limitations for realistic application exploration.  相似文献   

5.
As an alternative to single crystal silicon photovoltaics, thin film solar cells have been extensively explored for miniaturized cost-effective photovoltaic systems. Though the fight to gain efficiency has been severely engaged over the years, the battle is not yet over. In this review, we comb the fields to elucidate the strategies towards high efficiency thin films solar cells and provide pointers for further development. Starting from the photoelectron generation, we look into the fundamental issues in photoelectric conversion processes, including light harvesting and charge handling (separations, transportations and collections). The emerging organic-inorganic halide perovskite systems, as well as the rapidly developed polycrystalline inorganic systems, organic photovoltaics and amorphous silicon cells are discussed in details. The biggest bottleneck for the cost-effective polycrystalline inorganic cells is the composition sensitivity and deep defects; for amorphous silicon cells, it is the quantum of the dangling bonds; for organic cells, it is the low charge carrier mobility and high exciton binding energy; and for perovskite cells, it is the environmental degradation and the controversial mechanisms of generation of I-V hysteresis. Strategies of light harvesting and charge handling as well as directions to break the bottlenecks are pointed out.  相似文献   

6.
7.
Metal-organic coordination networks (MOCNs) have attracted wide interest because they provide a novel route towards porous materials that may find applications in molecular recognition, catalysis, gas storage and separation. The so-called rational design principle-synthesis of materials with predictable structures and properties-has been explored using appropriate organic molecular linkers connecting to metal nodes to control pore size and functionality of open coordination networks. Here we demonstrate the fabrication of surface-supported MOCNs comprising tailored pore sizes and chemical functionality by the modular assembly of polytopic organic carboxylate linker molecules and iron atoms on a Cu(100) surface under ultra-high-vacuum conditions. These arrays provide versatile templates for the handling and organization of functional species at the nanoscale, as is demonstrated by their use to accommodate C(60) guest molecules. Temperature-controlled studies reveal, at the single-molecule level, how pore size and chemical functionality determine the host-guest interactions.  相似文献   

8.
Advanced battery systems with high energy density have attracted enormous research enthusiasm with potential for portable electronics, electrical vehicles, and grid-scale systems. To enhance the performance of conversion-type batteries, various catalytic materials are developed, including metals and transition-metal dichalcogenides (TMDs). Metals are highly conductive with catalytic effects, but bulk structures with low surface area result in low atom utilization, and high chemical reactivity induces unfavorable dendrite effects. TMDs present chemical adsorption with active species and catalytic activity promotes conversion processes, suppressing shuttle effect and improving energy density. But they suffer from inferior conductivity compared with metal, and limited sites mainly concentrate on edges and defects. Single-atom materials with atomic sizes, good conductivity, and individual sites are promising candidates for advanced batteries because of a large atom utilization, unsaturated coordination, and unique electronic structure. Single-atom sites with high activity chemically trap intermediates to suppress shuttle effects and facilitate electron transfer and redox reactions for achieving high capacity, rate capability, and conversion efficiency. Herein, single-atom catalytic electrodes design for advanced battery systems is addressed. Major challenges and promising strategies concerning electrochemical reactions, theoretical model, and in situ characterization are discussed to shed light on future research of single-atom material-based energy systems.  相似文献   

9.
Ordered molecular materials are increasingly used in active electronic and photonic organic devices. In this progress report we discuss whether the self‐assembling properties and supramolecular structures of liquid crystals can be tailored to improve such devices. Recent developments in charge‐transporting and luminescent liquid crystals are discussed in the context of material requirements for organic light‐emitting devices, photovoltaics, and thin film transistors. We identify high carrier mobility, polarized emission, and enhanced output‐coupling as the key advantages of nematic and smectic liquid crystals for electroluminescence. The formation of anisotropic polymer networks gives the added benefits of multilayer capability and photopatternability. The anisotropic transport and high carrier mobilities of columnar liquid crystals make them promising candidates for photovoltaics and transistors. We also outline some of the issues in material design and processing that these applications demand. The photonic properties of chiral liquid crystals and their use as mirror‐less lasers are also discussed.  相似文献   

10.
Molecular self‐assembly constitutes a versatile strategy for creating functional structures on surfaces. Tuning the subtle balance between intermolecular and molecule‐surface interactions allows structure formation to be tailored at the single‐molecule level. While metal surfaces usually exhibit interaction strengths in an energy range that favors molecular self‐assembly, dielectric surfaces having low surface energies often lack sufficient interactions with adsorbed molecules. As a consequence, application‐relevant, bulk insulating materials pose significant challenges when considering them as supporting substrates for molecular self‐assembly. Here, the current status of molecular self‐assembly on surfaces of wide‐bandgap dielectric crystals, investigated under ultrahigh vacuum conditions at room temperature, is reviewed. To address the major issues currently limiting the applicability of molecular self‐assembly principles in the case of dielectric surfaces, a systematic discussion of general strategies is provided for anchoring organic molecules to bulk insulating materials.  相似文献   

11.
Materials for organic electronics are presently used in prominent applications, such as displays in mobile devices, while being intensely researched for other purposes, such as organic photovoltaics, large‐area devices, and thin‐film transistors. Many of the challenges to improve and optimize these applications are material related and there is a nearly infinite chemical space that needs to be explored to identify the most suitable material candidates. Established experimental approaches struggle with the size and complexity of this chemical space. Herein, the development of simulation methods is addressed, with a particular emphasis on predictive multiscale protocols, to complement experimental research in the identification of novel materials and illustrate the potential of these methods with a few prominent recent applications. Finally, the potential of machine learning and methods based on artificial intelligence is discussed to further accelerate the search for new materials.  相似文献   

12.
Outstanding functional tunability underpinning metal–organic framework (MOF) confers a versatile platform to contrive next‐generation chemical sensors, optoelectronics, energy harvesters, and converters. A rare exemplar of a porous 2D nanosheet material constructed from an extended 3D MOF structure is reported. A rapid supramolecular self‐assembly methodology at ambient conditions to synthesize readily exfoliatable MOF nanosheets, functionalized in situ by adopting the guest@MOF (host) strategy, is developed. Nanoscale confinement of light‐emitting molecules (as functional guest) inside the MOF pores generates unusual combination of optical, electronic, and chemical properties, arising from the strong host–guest coupling effects. Highly promising photonics‐based chemical sensing opened up by the new guest@MOF composite systems is shown. By harnessing host–guest optochemical interactions of functionalized MOF nanosheets, detection of an extensive range of volatile organic compounds and small molecules important for many practical applications has been accomplished.  相似文献   

13.
Chlorophylls are one of the most abundant organic pigments on the earth, which play an important role in the photosynthesis of plants, algae and bacteria. With the development of chromatography and chemical synthesis technology, many new chlorophylls from nature have been identified, and similar typical heterocyclic macrocyclic chlorophyll derivatives have also been designed and synthesized. Their chemical structures have significantly affected the absorption of light, energy transfer efficiency, excited-state lifetime, etc. Inspired by the chlorophylls interactions in chloroplasts for light-harvesting, we realized that intramolecular assembly and the resultant nanostructures played a more prominent role in their photophysical and photochemical properties, even in further biomedical applications, such as photodynamic and photothermal therapy, photocatalytic diagnosis, as well as optical, photoacoustic, magnetic resonance and nuclear medical imaging. In this review, we discuss the photo-properties of chlorophylls, overview the driving forces of assembly, and summarize biomedical-relevant advantages incorporated supramolecular nanostructures. In particular, the dynamic assembly under physiological condition provides unpredictable and interesting biological effects, such as aggregation/assembly induced drug retention in disease areas, optimized biodistribution and optimized the pharmacokinetics. The labeling on the assembly also provides a useful tool for us to observe the self-assembled nanostructures in vivo in a non-invasive way. Through the elaboration of different examples of chlorophylls, we hope to provide some inspiration for the biomedical application design of chlorophylls derivatives.  相似文献   

14.
Transition-metal oxides improve power conversion efficiencies in organic photovoltaics and are used as low-resistance contacts in organic light-emitting diodes and organic thin-film transistors. What makes metal oxides useful in these technologies is the fact that their chemical and electronic properties can be tuned to enable charge exchange with a wide variety of organic molecules. Although it is known that charge exchange relies on the alignment of donor and acceptor energy levels, the mechanism for level alignment remains under debate. Here, we conclusively establish the principle of energy alignment between oxides and molecules. We observe a universal energy-alignment trend for a set of transition-metal oxides--representing a broad diversity in electronic properties--with several organic semiconductors. The trend demonstrates that, despite the variance in their electronic properties, oxide energy alignment is governed by one driving force: electron-chemical-potential equilibration. Using a combination of simple thermodynamics, electrostatics and Fermi statistics we derive a mathematical relation that describes the alignment.  相似文献   

15.
Recent interest in flexible electronics has led to a paradigm shift in consumer electronics, and the emergent development of stretchable and wearable electronics is opening a new spectrum of ubiquitous applications for electronics. Organic electronic materials, such as π‐conjugated small molecules and polymers, are highly suitable for use in low‐cost wearable electronic devices, and their charge‐carrier mobilities have now exceeded that of amorphous silicon. However, their commercialization is minimal, mainly because of weaknesses in terms of operational stability, long‐term stability under ambient conditions, and chemical stability related to fabrication processes. Recently, however, many attempts have been made to overcome such instabilities of organic electronic materials. Here, an overview is provided of the strategies developed for environmentally robust organic electronics to overcome the detrimental effects of various critical factors such as oxygen, water, chemicals, heat, and light. Additionally, molecular design approaches to π‐conjugated small molecules and polymers that are highly stable under ambient and harsh conditions are explored; such materials will circumvent the need for encapsulation and provide a greater degree of freedom using simple solution‐based device‐fabrication techniques. Applications that are made possible through these strategies are highlighted.  相似文献   

16.
This review surveys the work developed in the field of functional hybrid materials, especially those containing conducting organic polymers (COPs), in combination with a variety of inorganic species, from molecular to extended phases, including clusters and nano‐sized inorganic particles. Depending on the dominating structural matrix, we distinguish and analyze organic–inorganic (OI) hybrids, nanocomposite materials, and inorganic–organic (IO) phases. These materials have been used in a wide variety of applications, including energy‐storage applications, electrocatalysis, the harnessing of electrochromic and photoelectrochromic properties, application in display devices, photovoltaics, and novel energy‐conversion systems, proton‐pump electrodes, sensors, or chemiresistive detectors, which work as artificial “noses”.  相似文献   

17.
We present a critical review of semiconducting/light emitting, liquid crystalline materials and their use in electronic and photonic devices such as transistors, photovoltaics, OLEDs and lasers. We report that annealing from the mesophase improves the order and packing of organic semiconductors to produce state-of-the-art transistors. We discuss theoretical models which predict how charge transport and light emission is affected by the liquid crystalline phase. Organic photovoltaics and OLEDs require optimization of both charge transport and optical properties and we identify the various trade-offs involved for ordered materials. We report the crosslinking of reactive mesogens to give pixellated full-colour OLEDs and distributed bi-layer photovoltaics. We show how the molecular organization inherent to the mesophase can control the polarization of light-emitting devices and the gain in organic, thin-film lasers and can also provide distributed feedback in chiral nematic mirrorless lasers. We update progress on the surface alignment of liquid crystalline semiconductors to obtain monodomain devices without defects or devices with spatially varying properties. Finally the significance of all of these developments is assessed.  相似文献   

18.
Incorporating narrow‐bandgap near‐infrared absorbers as the third component in a donor/acceptor binary blend is a new strategy to improve the power conversion efficiency (PCE) of organic photovoltaics (OPV). However, there are two main restrictions: potential charge recombination in the narrow‐gap material and miscompatibility between each component. The optimized design is to employ a third component (structurally similar to the donor or acceptor) with a lowest unoccupied molecular orbital (LUMO) energy level similar to the acceptor and a highest occupied molecular orbital (HOMO) energy level similar to the donor. In this design, enhanced absorption of the active layer and enhanced charge transfer can be realized without breaking the optimized morphology of the active layer. Herein, in order to realize this design, two new narrow‐bandgap nonfullerene acceptors with suitable energy levels and chemical structures are designed, synthesized, and employed as the third component in the donor/acceptor binary blend, which boosts the PCE of OPV to 11.6%.  相似文献   

19.
Research on microporous materials, hollow solids with channels and cavities that include small guest molecules, has advanced in fundamental and applied aspects during 1999–2000. The retrosynthesis of crystal structures in terms of robust supramolecular synthons (recognition motifs) and functionalised organic molecules (building blocks) has led to the design of new porous architectures and modification in the properties of existing host materials. Even as conventional O–H⋯O and N–H⋯O hydrogen bonds continue to be used to attain these goals, weak hydrogen bonds and heteroatom interactions, such as C–H⋯O, halogen⋯halogen, strengthened by multi-point recognition and cooperativity effects, have emerged in new design strategies. A proper understanding of pseudopolymorphism, the phenomenon of solvent inclusion in crystals, will promote the next phase of host–guest research.  相似文献   

20.
Smart materials are those materials that are responsive to chemical (organic molecules, chemical agents or specific agents), biochemical (protein, enzymes, growth factors, substrates or ligands), physical (electric field, magnetic field, temperature, pH, ionic strength or radiation) or mechanical (pressure or mechanical stress) signals. These responsive materials interact with the stimuli by changing their properties or conformational structures in a predictable manner. Recently, smart polymers have been utilized in various biomedical applications. Particularly, they have been used as a platform to synthesize stimuli-responsive systems that could deliver therapeutics to a specific site for a specific period with minimal adverse effects. For instance, stimuli-responsive polymers-based systems have been recently reported to deliver different bioactive molecules such as carbohydrates (heparin), chemotherapeutic agents (doxorubicin), small organic molecules (anti-coagulants), nucleic acids (siRNA), and proteins (growth factors and hormones). Protein therapeutics played a fundamental role in treatment of various chronic and some autoimmune diseases. For instance insulin has been used in treatment of diabetes. However, being a protein in nature, insulin delivery is limited by its instability, short half-life, and easy denaturation when administered orally. To overcome these challenges, and as highlighted in this review article, much research efforts have been recently devoted to design and develop convenient smart controlled nanosystems for protein therapeutics delivery.  相似文献   

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