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Exploiting narrow-bandwidth-emission fluorescent materials is crucial for next-generation wide-color gamut displays. Inspired by the narrow-bandwidth-emission characteristic of chlorophyll derivates, the present work develops a facile strategy to synthesize a series of red-emitting chlorophyll-structured CDs (CHL-CDs) with ultra-high color purity and good carrier mobility from different traditional Chinese medicine leaves through a simple cross-linking polymerization and carbonization process. The obtained CHL-CDs exhibit bright photoluminescence centered at 671 nm, ultra-high color purity with an FWHM of 23 nm, and a high photoluminescence quantum yield of up to 62%. More importantly, based on in-depth experimental and theoretical studies on the macroscopic host–guest interactions and microscopic interfacial interactions between the CHL-CDs and charge transporting materials, high-performance red electroluminescent light-emitting diodes are successfully prepared, with FWHM of only 28 nm, turn-on voltage of 3.7 V, maximum luminance of 623 cd m−2, and maximum current efficiency of 0.26 cd A−1. This study provides a universal platform for fabricating narrow-bandwidth-emission CDs with significant applications in photoelectric devices. [ABSTRACT FROM AUTHOR]

Two kinds of triphenylamine‐derived solid‐state 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−2, high current efficiency of 1.57/2.34 cd A−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 solid‐state emissive CDs with significant applications in photoelectric device. [ABSTRACT FROM AUTHOR]

When it comes to building high-efficiency thin-film optoelectronic devices, we are constantly striving to improve the efficiency of charge transport and injection. Device performance is hampered by the low mobility and injection ability of organic charge transporting materials that are routinely used. In this paper, we show that instead of using organics as a hole transporting layer, metal halide perovskite can be used to fabricate high-efficiency carbon dots-based light-emitting diodes for the first time. The organic light-emitting layer and the underlying perovskite layer combine to form an organic–inorganic perovskite planar heterojunction, and the sufficient contact at the junction takes advantage of the high charge mobility of perovskite, facilitating the hole transportation and injection. Moreover, the interaction between perovskite and the organic emitting layer can be engineered via manipulating the halogenic component, thickness, surface morphology, etc., contributing to the device optimization and the understanding of the carrier kinetics in this unique organic–inorganic hybrid optoelectronic device. Our work comprehensively evaluates the full potentials of metal halide perovskite as a hole transporting layer by uncovering the positive effect on hole transportation and injection. As a consequence, our findings open up new avenues for the development of efficient carbon dot-based light-emitting diodes. [ABSTRACT FROM AUTHOR]

• An oil-soluble fluorescent CDs (TPA-CDs) is synthesized through a solvent-free reaction. • Solvent-free synthesized CDs are used for both photoluminescent and electroluminescent LEDs. • A maximum luminance of 1503 cd·m−2 is achieved for TPA-CDs based electroluminescent LEDs. • Photoluminescent TPA-CDs LEDs can be easily assembled with oil soluble resin. Fluorescent carbon dots (CDs) have attracted great attention in multidisciplinary fields due to their distinctive advantages of tunable emission, low toxicity and abundant raw materials. However, it is still a big challenge to effectively applicate these CDs in electroluminescent light-emitting diodes (LEDs) due to their poor oil solubility and easy aggregation-induced quenching. Herein, an oil-soluble fluorescent CDs is designed and synthesized using triphenylamine and 4-iodophenyldiphenylamine as precursors through a solvent-free reaction. The obtained CDs (TPA-CDs) display an emission peak at 551 nm with good oil-solubility in different organic solvents. Therefore, TPA-CDs can be used as the host material of emission layer to prepare monochromatic electroluminescent LEDs with a maximum luminance of 227 cd·m−2 and as guest material in PVK to demonstrate white light electroluminescent LED with a maximum luminance of 1503 cd·m−2. This CDs can also be mixed well with oil soluble resin to easily assemble photoluminescent devices with a high luminous efficiency of 17.1 lm·W−1. This is the first example that solvent-free synthesized CDs are used for both photoluminescent and electroluminescent devices. [ABSTRACT FROM AUTHOR]