Red Phosphorescent Carbon Quantum Dot Organic Framework-Based Electroluminescent Light-Emitting Diodes Exceeding 5% External Quantum Efficiency

Abstract

Carbon quantum dots (CQDs) have developed into prospective nanomaterials for next-generation lighting and displays due to their intrinsic advantages of high stability, low cost, and environmental friendliness. However, confined by the spin-forbidden nature of triplet state transitions, the highest theoretical value of external quantum efficiency (EQE) of fluorescent CQDs is merely 5%, which fundamentally limits their further application in electroluminescent light-emitting diodes (LEDs). Soluble phosphorescent CQDs offer a means of breaking the shackle to achieve efficient monochromatic electroluminescence, especially red emission, which is a pivotal constituent in full-color displays. Here, the synthesis of red (625 nm) phosphorescent carbon quantum dot organic frameworks (CDOFs) with a quantum yield of up to 42.3% and realization of high-efficiency red phosphorescent electroluminescent LEDs are reported. The LEDs based on the CDOFs exhibited a red emission with a maximum luminance of 1818 cd m −2 and an EQE of 5.6%. This work explores the possibility of a new perspective for developing high-performance CQD-based electroluminescent LEDs.

Lecithin Capping Ligands Enable Ultrastable Perovskite-Phase CsPbI3 Quantum Dots for Rec. 2020 Bright-Red Light-Emitting Diodes

“…There are only a few publications on bright-red LEDs based on CsPbI 3 QDs with electroluminescence wavelengths shorter than 635 nm, and the best of those reported LEDs (see Supporting Information Table T1) exhibited an external quantum efficiency (EQE) of 6.4%. , Among lead-free materials for bright-red LEDs, Sn-based perovskites display a narrow emission (FWHM 21 nm), but their devices exhibit a low EQE of 5%. − We note that both green and deep-red LEDs of lead halide perovskite QDs achieved considerable success, showcasing EQEs exceeding 20%. ,, In contrast, bright-red LEDs of CsPbI 3 QDs raise new challenges with phase degradation, spectral instability, low EQE, and poor operational stability. , …”

Synthesis, optical properties and applications of red/near-infrared carbon dots

“…3a and b, the exciton dynamics might be mainly determined by the core size/composition, the presence of dopants and surface functional groups. 23,25,[40][41][42]44,45,89,94,113,135,[150][151][152][153] As discussed before, one way to obtain red/NIR C-dots is to improve the carbonization of the C-dots themselves, 135 which can contribute to the creation of highly crystalline C-dots wihtout surface defects, leading to a band-gap emission (Fig. 3a and b, left).…”

“…27–35 Thanks to the above-mentioned properties, C-dots have been widely used as building blocks for the design of new types of solar cells, catalysts, LSCs, LEDs and bio-applications, such as deep-tissue imaging, biosensing, nanothermometry, and biomedicine (see Scheme 1). 18,20,22–25,27–30,32,33,36–91…”

Physical Mechanism of Fluorescence and Chirality of Functionalized Graphene Quantum Dots

“…Generally, CDs are regarded as small carbon nanoparticles in aqueous or other suspensions, which are of three types: (I) graphene quantum dots (GQDs), (II) carbon nanodots, and (III) carbon polymeric dots. − Their optical, electronic, and catalytic properties are also hinged on their different structures . Because of the different structures of the CDs, several synthesis routes can be commonly classified into “bottom-up” strategies and “top-down” strategies. − As an emerging material, CD exhibits a lot of excellent advantages, such as low cytotoxicity, good biocompatibility, stable chemical inertness, efficient light harvesting, and outstanding photoinduced electron transfer, , thus resulting in a wide range of applications in bioimaging, , biosensors, − photocatalysis, sensors, optoelectronic devices, , solar cells, , and so forth.…”