Fluorescent carbon dots (CDs) have recently become a research hotspot in multidisciplinary fields owing to their distinctive advantages, including outstanding photoluminescence properties, high biocompatibility, low toxicity, and abundant raw materials. Among the promising CDs, narrow‐bandwidth emissive CDs with high color purity have emerged as a rising star in recent years because of their significant potential applications in bioimaging, information sensing, and photoelectric displays. In this review, the state‐of‐the‐art advances of narrow‐bandwidth emissive CDs are systematically summarized, and the factors influencing the emission bandwidth, preparation methods, and applications of narrow‐bandwidth emissive CDs are described in detail. Besides, existing challenges and future perspectives for achieving high‐performance narrow‐bandwidth emissive CDs are also discussed. This overview paper is expected to generate more interest and promote the rapid development of this significant research area.

Interface modification to minimize charge recombination and trapping for efficient charge transport is crucial for the performance of perovskite solar cells (PSCs). Herein, functionalized p‐type blue carbon dots (B‐CDs) are ventured as an interface passivation layer to enhance the efficiency and long‐term stability of all‐inorganic CsPbI2Br PSCs. It is found that first the blue carbon dots with abundant NH, CN, CO, and CO functional groups effectively passivate defects by reacting with I− and Pb2+ ions in the perovskite through hydrogen and coordinative bonds. Second, the p‐type B‐CDs modifiers form a P–N junction with the n‐type perovskite to provide efficient pathways for hole transfer and electron blocking. Third, the B‐CDs increase the hydrophobicity of the perovskite film to improve the stability of CsPbI2Br PSCs. With the above advantages, the CsPbI2Br PSC with B‐CDs modification shows an efficiency as high as 16.76%, one of the highest for its type. In addition, the modification renders significant improvement of air and light stability, with 95.33% of the initial PCE retained after storage in the ambient environment for 1000 h. This work demonstrates the great potential of B‐CDs application in perovskite‐based optoelectronic devices.

The solutionprocessed perovskite is mostly polycrystalline with a large number of grain boundaries (GBs) that induce the fastest ion migration than other sites. [5][6][7][8][9] Meanwhile, the GBs are the dominating attack sites of water and oxygen, which will deteriorate the operation stability of PerSCs. [10][11][12][13][14] Therefore, high-grade perovskite films with high coverage, ideal crystal morphology, good crystallinity, and few defects are crucial for fabricating high-performance PerSCs. [15,16] Plentiful reports have shown that introducing functional additives into perovskite precursor solution can affect the nucleation rate, film morphology, grain size, and crystallinity of perovskite. Precursor additives, such as dimethyl sulfoxide, acids or 2D perovskite, play a vital role in the film formation of perovskite, determining the photovoltaic performance of PerSCs. [17][18][19][20][21] In 2015, Yan et al. revealed that the precursor of MAPbI 3 is a colloid state rather than a real solution. The addition of methylammonium iodide and methylamine chloride leads to a facilitated aggregation of lead iodide, which effectively improves the crystallinity of the perovskite film and ultimately yields promoted PCEs in PerSCs. [22] Ran et al. found that PbI 2 colloid has a wider particle size distribution and larger colloid under certain acidic conditions. [23] Liang et al. proposed an effective cosolvent strategy by introducing ethyl alcohol into the perovskite ink to construct high-performance, blade-coated PerSC modules. [4] Furthermore, the latest reports shed new light on controlling crystallization in 2D perovskites. A 2D (NpMA) 2 PbI 4 perovskite was incorporated into the PbI 2 precursor to modify the crystal growth process in 2D/3D perovskite film using a two-step deposition method. [24] Luo and his coworkers introduced highly oriented 2D (BDA)PbI 4 perovskites as seeds to chalk up large size colloids, which can optimize the growth kinetics of 3D perovskite and make its crystallization directly stride over the nucleation stage. [25] The introduction of these crystal auxiliary components has been proved to be a practical approach to modifying the grain size of perovskite films, while a synergistic function in inhibiting the formation of GBs Crystal growth regulation has become an effective solution to reduce the defects at grain boundaries (GBs) and surfaces of perovskite films for better photovoltaic performances. Oxime acid materials are maturely used as selective collectors in the flotation separation of oxide minerals. Such materials, showing a strong coordination effect and high selectivity with lead, may have great potential in controlling the crystal growth and passivating the defect of perovskite film, which are rarely applied in perovskite solar cells (PerSCs). Herein, an oxime acid-based material with multi-coordination sites, ethyl 2-(2-aminothiazole-4-yl)-2-hydroxyiminoacetate (EHA), is incorporated into the PbI 2 precursor solution to fabricate high-performance PerSCs using a two-step method. The ...

Carbon dot (CD)-based room temperature phosphorescence nanomaterials are currently drawing enormous attention. However, constructing fluorescence–phosphorescence dual emissive CDs (FP-CDs) is still a huge challenge due to the limited preparation strategies....

Electrochemical reactions occur on the surface of the electrode, so electrode modifications are essential for redox flow batteries (RFBs). Major works regarding electrode modifications focus on traditional RFBs like vanadium systems, but minor works stress on organic RFBs that represent a rapidly developed technology for large-scale energy storage. In this work, we employ thermal oxidation (600 °C) and investigate the effect of the heating time on a polyacrylonitrile-based carbon felt used in 2,6-dihydroxyanthraquinone (2,6-DHAQ)/K 4 Fe(CN) 6 RFBs. The structure of the carbon felt is characterized by thermogravimetric analysis, scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy methods. The electrochemical properties of 2,6-DHAQ are studied by cyclic voltammetry analysis. It is found that, when the heating time is set at 2.0 h, 2,6-DHAQ/K 4 Fe(CN) 6 RFBs exhibit a lower capacity decay rate at 0.0287% per cycle in 200 cycles, which is 3 times lower than the other cases. The results from 1 H nuclear magnetic resonance spectra unveil that the lower capacity loss is achieved by converting the byproduct anthrone back into 2,6-DHAQ at a slight cost of reducing Coulombic efficiency. Our work unambiguously demonstrates that the lifetime of anthraquinone-based RFBs can be effectively extended via thermal modification of electrodes.