Carbon dots (C-Dots), defined by characteristic sizes of <10 nm, have become a rising star in carbon nanomaterials. C-Dots possess many unique physiochemical and photochemical properties which make ...them a promising platform for imaging, environmental, catalytic, biological and energy-related applications. To date, C-Dots have been investigated extensively, and their related applications have developed rapidly. However, quantitative understanding of the physiochemical properties of C-Dots still remains a difficult challenge because of their complex structures. Here, we will highlight the recent progress in the practical applications of C-Dots, with particular attention to the research in light-emitting devices, bioimaging and biodetection, catalysis, functional materials, and agriculture.
We highlight the recent progress in the practical applications of C-Dots, with particular attention to the research in light-emitting devices, bioimaging and biodetection, catalysis, functional materials, and agriculture.
Organometal halide perovskites quantum dots (OHP‐QDs) with bright, color‐tunable, and narrow‐band photoluminescence have significant advantages in display, lighting, and laser applications. Due to ...sparse concentrations and difficulties in the enrichment of OHP‐QDs, production of large‐area uniform films of OHP‐QDs is a challenging task, which largely impedes their use in electroluminescence devices. Here, a simple dip‐coating method has been reported to effectively fabricate large‐area uniform films of OHP‐QDs. Using this technique, multicolor OHP‐QDs light‐emitting diodes (OQ‐LEDs) emitting in blue, blue‐green, green, orange, and red color have been successfully produced by simply tuning the halide composition or size of QDs. The blue, green, and red OQ‐LEDs exhibited, respectively, a maximum luminance of 2673, 2398, and 986 cd m−2 at a current efficiency of 4.01, 3.72, and 1.52 cd A−1, and an external quantum efficiency of 1.38%, 1.06%, and 0.53%, which are much better than most LEDs based on OHP films. The packaged OQ‐LEDs show long‐term stability in air (humidity ≈50%) for at least 7 d. The results demonstrate the great potential of the dip‐coating method to fabricate large‐area uniform films for various QDs. The high‐efficiency OQ‐LEDs also demonstrate the promising potential of OHP‐QDs for low‐cost display, lighting, and optical communication applications.
Organometal halide perovskite quantum dot (OHP‐QDs)‐based light‐emitting diodes (LEDs) are developed using a simple dip‐coating method. The OHP‐QDs‐based LEDs show multicolor emission from blue, green to red by tuning the composition or size of the OHP‐QDs. The packaged devices also exhibit robust stability under continuous bias in air for at least 7 d.
Semiconductor nanowires are attracting intense interest as a promising material for solar energy conversion for the new‐generation photovoltaic (PV) technology. In particular, silicon nanowires ...(SiNWs) are under active investigation for PV applications because they offer novel approaches for solar‐to‐electric energy conversion leading to high‐efficiency devices via simple manufacturing. This article reviews the recent developments in the utilization of SiNWs for PV applications, the relationship between SiNW‐based PV device structure and performance, and the challenges to obtaining high‐performance cost‐effective solar cells.
Silicon nanowires (SiNWs) are attracting intense interest as a promising material for solar energy conversion for the new‐generation photovoltaic (PV) technology. This article reviews recent developments in the utilization of SiNWs for PV applications, the relationship between SiNW‐based PV device structure and performance, and the challenges to obtaining high‐performance cost‐effective solar cells.
Perovskite light‐emitting diodes (PeLEDs) show great application potential in high‐quality flat‐panel displays and solid‐state lighting due to their steadily improved efficiency, tunable colors, ...narrow emission peak, and easy solution‐processing capability. However, because of high optical confinement and nonradiative charge recombination during electron–photon conversion, the highest reported efficiency of PeLEDs remains far behind that of their conventional counterparts, such as inorganic LEDs, organic LEDs, and quantum‐dot LEDs. Here a facile route is demonstrated by adopting bioinspired moth‐eye nanostructures at the front electrode/perovskite interface to enhance the outcoupling efficiency of waveguided light in PeLEDs. As a result, the maximum external quantum efficiency and current efficiency of the modified cesium lead bromide (CsPbBr3) green‐emitting PeLEDs are improved to 20.3% and 61.9 cd A−1, while retaining spectral and angular independence. Further reducing light loss in the substrate mode using a half‐ball lens, efficiencies of 28.2% and 88.7 cd A−1 are achieved, which represent the highest values reported to date for PeLEDs. These results represent a substantial step toward achieving practical applications of PeLEDs.
Highly efficient perovskite light‐emitting diodes are achieved by implementing a simple and cost‐effective method for efficient outcoupling of waveguided light. A record external quantum efficiency of 28.2% is realized for the device based on cesium lead bromide (CsPbBr3), while retaining the same spectral response for broad viewing angles.
Self‐healing is the way by which nature repairs damage and prolongs the life of bio entities. A variety of practical applications require self‐healing materials in general and self‐healing polymers ...in particular. Different (complex) methods provide the rebonding of broken bonds, suppressing crack, or local damage propagation. Here, a simple, versatile, and cost‐effective methodology is reported for initiating healing in bulk polymers and self‐healing and anticorrosion properties in polymer coatings: introduction of carbon dots (CDs), 5 nm sized carbon nanocrystallites, into the polymer matrix forming a composite. The CDs are blended into polymethacrylate, polyurethane, and other common polymers. The healing/self‐healing process is initiated by interfacial bonding (covalent, hydrogen, and van der Waals bonding) between the CDs and the polymer matrix and can be optimized by modifying the functional groups which terminate the CDs. The healing properties of the bulk polymer–CD composites are evaluated by comparing the tensile strength of pristine (bulk and coatings) composites to those of fractured composites that are healed and by following the self‐healing of scratches intentionally introduced to polymer–CD composite coatings. The composite coatings not only possess self‐healing properties but also have superior anticorrosion properties compared to those of the pure polymer coatings.
This work utilizes a novel, simple, and versatile approach to produce self‐healing polymers by introduction of surface functionalized carbon dots to the polymer. The concept is successfully validated for several common bulk polymers and standard polymer coatings. The introduction of carbon dots not only induces self‐healing but also significantly improves the anticorrosion resistance of the polymer coatings.
Ammonia–borane (AB) is an excellent material for chemical storage of hydrogen. However, the practical utilization of AB for production of hydrogen is hindered by the need of expensive noble ...metal‐based catalysts. Here, we report CuxCo1−xO nanoparticles (NPs) facilely deposited on graphene oxide (GO) as a low‐cost and high‐performance catalyst for the hydrolysis of AB. This hybrid catalyst exhibits an initial total turnover frequency (TOF) value of 70.0 (H2) mol/(Cat‐metal) mol⋅min, which is the highest TOF ever reported for noble metal‐free catalysts, and a good stability keeping 94 % activity after 5 cycles. Synchrotron radiation‐based X‐ray absorption spectroscopy (XAS) investigations suggested that the high catalytic performance could be attributed to the interfacial interaction between CuxCo1−xO NPs and GO. Moreover, the catalytic hydrolysis mechanism was studied by in situ XAS experiments for the first time, which reveal a significant water adsorption on the catalyst and clearly confirm the interaction between AB and the catalyst during hydrolysis.
A synergistic catalyst of CuxCo1−xO nanoparticles on graphene oxide achieves a TOF value of 70.0 (H2) mol/(Cat‐metal) mol⋅min for the hydrolysis of ammonia–borane, which is the highest value ever reported for noble‐metal‐free catalysts. The hydrolysis mechanism was also studied by in situ XAS experiments for the first time.
A facile ultrasonic route for the fabrication of graphene quantum dots (GQDs) with upconverted emission is presented. The as-prepared GQDs exhibit an excitation-independent downconversion and ...upconversion photoluminescent (PL) behavior, and the complex photocatalysts (rutile TiO2/GQD and anatase TiO2/GQD systems) were designed to harness the visible spectrum of sunlight. It is interesting that the photocatalytic rate of the rutile TiO2/GQD complex system is ca. 9 times larger than that of the anatase TiO2/GQD complex under visible light (λ > 420 nm) irradiation in the degradation of methylene blue.
Organic semiconductors can be designed and constructed in π‐stacked structures instead of the conventional π‐conjugated structures. Through‐space interaction (TSI) occurs in π‐stacked optoelectronic ...materials. Thus, unlike electronic coupling along the conjugated chain, the functional groups can stack closely to facilitate spatial electron communication. Using π‐stacked motifs, chemists and materials scientists can find new ways for constructing materials with aggregation‐induced emission (AIE), thermally activated delayed fluorescence (TADF), circularly polarized luminescence (CPL), and room‐temperature phosphorescence (RTP), as well as enhanced molecular conductance. Organic optoelectronic devices based on π‐stacked molecules have exhibited very promising performance, with some of them exceeding π‐conjugated analogues. Recently, reports on various organic π‐stacked structures have grown rapidly, prompting this review. Representative molecular scaffolds and newly developed π‐stacked systems could stimulate more attention on through‐space charge transfer the well‐known through‐bond charge transfer. Finally, the opportunities and challenges for utilizing and improving particular materials are discussed. The previous achievements and upcoming prospects may provide new insights into the theory, materials, and devices in the field of organic semiconductors.
Unlike traditional covalent bond‐connected conjugated molecules, π‐stacked small molecules have special advantages in organic semiconductors. This review mainly focuses on the research development of π‐stacked molecular systems and introduces the new characteristics brought by the special molecular configuration and its application in organic semiconductors.
As an interesting layered material, molybdenum disulfide (MoS2) has been extensively studied in recent years due to its exciting properties. However, the applications of MoS2 in optoelectronic ...devices are impeded by the lack of high‐quality p–n junction, low light absorption for mono‐/multilayers, and the difficulty for large‐scale monolayer growth. Here, it is demonstrated that MoS2 films with vertically standing layered structure can be deposited on silicon substrate with a scalable sputtering method, forming the heterojunction‐type photodetectors. Molecular layers of the MoS2 films are perpendicular to the substrate, offering high‐speed paths for the separation and transportation of photo‐generated carriers. Owing to the strong light absorption of the relatively thick MoS2 film and the unique vertically standing layered structure, MoS2/Si heterojunction photodetectors with unprecedented performance are actualized. The self‐driven MoS2/Si heterojunction photodetector is sensitive to a broadband wavelength from visible light to near‐infrared light, showing an extremely high detectivity up to ≈1013 Jones (Jones = cm Hz1/2 W−1), and an ultrafast response speed of ≈3 μs. The performance is significantly better than the photodetectors based on mono‐/multilayer MoS2 nanosheets. Additionally, the MoS2/Si photodetectors exhibit excellent stability in air for a month. This work unveils the great potential of MoS2/Si heterojunction for optoelectronic applications.
A new type of visible–near infrared self‐driven photodetector is developed by sputtering a layer of n‐type MoS2 film with a vertically standing layered structure on p‐type silicon. With the advantages of easy fabrication, wide response spectrum, extremely high detectivity (≈1013 Jones), ultrafast response speed (≈3 μs), and good durability, this heterojunction photodetector shows great potential for optoelectronic applications.
High reflection and low build‐in electrical field hinder the power conversion efficiency (PCE) of planar n‐Si/organic solar cells. Depositing a thin layer of MoO3 can improve the performance by ...creating an antireflection layer on the front surface as well as inducing an inversion layer in the Si. The as‐processed device achieves a record PCE of 13.8%.
