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.

Lead‐free perovskite emitters, particularly 2D tin (Sn) halide perovskites, have attracted considerable academic attention in recent years. However, the problems of Sn oxidation and rapid crystallization lead to an inferior perovskite morphology with high trap states, thus limiting the luminous efficiency of Sn halide perovskite light‐emitting diodes (PeLEDs). In this study, the authors establish an approach by introducing an organic additive, 2–imidodicarbonic diamide (biuret), to address the issues of Sn oxidation and fast crystallization. The unique symmetrical carbonyl groups in the biuret robustly interact with the Sn‐I framework, providing a strong Sn‐anchoring effect. Consequently, it also suppresses the easy oxidation of Sn2+, regulating the crystallization process simultaneously. Density functional theory (DFT) calculations also confirmed the robust interaction between the biuret and the 2D Sn halide perovskite. Furthermore, the authors demonstrate efficient PeLEDs with saturated red emission at 637 nm, a maximum luminance (Lmax) of 418 cd m−2, a maximum external quantum efficiency (EQEmax) of 1.37%, and a half‐life (T50) of 288 s. This work provides insights on the microcosmic chemical interaction between organics and 2D Sn halide perovskites, advancing the development of efficient lead‐free PeLEDs.

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....

The reaction conditions of high temperature and high pressure will introduce structural defects, high energy consumption, and security risks, severely hindering the industrial application of organic carbon nanodots (CDs). Moreover, the aggregation caused quenching effect also fundamentally limits the CDs based electroluminescent light emitting diodes (LEDs). Herein, for the first time, a rapid one‐step room temperature synthetic strategy is introduced to prepare highly emissive solid‐state‐fluorescent CDs (RT‐CDs). A strong oxidizing agent, potassium periodate (KIO4), is adopted as a catalyst to facilitate the cyclization of o‐phenylenediamine and 4‐dimethylamino phenol in aqueous solution at room temperature for only 5 min. The resultant organic molecule, 2‐(dimethylamino) phenazine, will self‐assemble kinetically to generate supramolecular‐structure CDs during crystallization. The elaborately arranged supramolecular structure (J aggregates) endows CDs with intense solid‐state‐fluorescence. Density functional theory (DFT) calculation shows that the excited state of RT‐CDs exhibits charge transfer characteristic owing to the unique donor‐Π‐acceptor structure. A high‐performance monochrome RT‐CDs based electroluminescent LEDs (2967 cd m−2 and 1.38 cd A−1) were fabricated via systematic optimizations of device engineering. This work provides a concrete and feasible avenue for the rapid and massive preparation of CDs, advancing the commercialization of CDs based optoelectronic devices.

Two kinds of triphenylamine-derived solidstate emissive carbon dots (CDs) with orange and yellow color are facilely synthesized through solvothermal treatment, taking advantage of the nonplanar structure and good carrier mobility of triphenylamine unit. Theoretical calculations show that the triphenylamine structure could greatly inhibit the direct π-π stacking of aromatic skeletons and enhance the fluorescence properties of CDs in aggregation state. By adopting the CDs as single emissive layer, high-performance orange-color and green-color electroluminescent light-emitting diodes (LEDs) are successfully fabricated, with maximum brightness of 9450/4236 cd m À 2 , high current efficiency of 1.57/2.34 cd A À 1 and low turn-on voltage of 3.1/3.6 eV are respectively achieved. Significantly, white-color LED device is further prepared. This work provides a universal platform for the construction of novel solidstate emissive CDs with significant applications in photoelectric device.