High-performance Light-emitting Diodes Research Articles

Efficient and Near-Zero Thermal Quenching Cr3+-Doped Garnet-Type Phosphor for High-Performance Near-Infrared Light-Emitting Diode Applications.

In recent years, near-infrared (NIR) phosphors have attracted great research interest due to their unique physical properties and broad application prospects. However, obtaining NIR phosphors with both high quantum efficiency and excellent thermal stability remains a great challenge. In this study, novel NIR Ca3Mg2ZrGe3O12:Cr3+ phosphors were successfully prepared using a high-temperature solid-phase method, and the structure and luminescent properties of the material were systematically investigated. Ca3Mg2ZrGe3O12:0.01Cr3+ emits NIR light in the range of 600 to 900 nm with a peak at 758 nm and a half-height width of 89 nm under the excitation of 457 nm blue light. NIR luminescence shows considerable quantum efficiency, and the internal quantum efficiency of the optimized sample is up to 68.7%. Remarkably, the Ca3Mg2ZrGe3O12:0.01Cr3+ phosphor exhibits a near-zero thermal quenching behavior, and the luminescence intensity of the sample at 250 °C maintains 92% of its intensity at room temperature. The mechanism of high thermal stability has been elucidated by calculating the Huang Kun factor and activation energy. Finally, NIR pc-LED devices prepared from Ca3Mg2ZrGe3O12:0.01Cr3+ phosphor with commercial blue LED chips have good performance, proving that this Ca3Mg2ZrGe3O12:0.01Cr3+ NIR phosphor has potential applications in night vision and biomedical imaging.

High-efficiency RbASiF6:Mn4+ (A = K, Cs) phosphors obtained by one-step green synthesis method

Red-emitting Mn4+-doped fluoride phosphors are recognized as promising materials for high-performance warm white light-emitting diodes (WLEDs). However, the extensive use of toxic hydrofluoric acid in traditional synthesis methods hinders their development and commercialization. Furthermore, the traditional solid-phase method often has cumbersome sintering steps, high temperature, long holding time, and certain safety hazards, so it is very necessary to develop a green synthesis method with simple steps and low energy consumption. In this study, a low-temperature solid-state method is proposed to synthesize RbASiF6:Mn4+ (A = K, Cs) phosphors by one step. Optimal emission intensities were observed at Mn4+ concentrations of 1.2% in RbKSiF6 and 2.1% in RbCsSiF6. These phosphors demonstrated high thermal stability. At 423K, the photoluminescence intensities of RbKSiF6:1.2%Mn4+ and RbCsSiF6:2.1%Mn4+ reached 114% and 87% of their respective values at room temperature. Meanwhile, the chromaticity shifts were almost negligible, and high color purity was achieved for both phosphors. The electro-optical performance of WLED devices utilizing these phosphors, in combination with YAG:Ce3+ and GaN chips, showed high color rendering indices (CRI) and low correlated color temperatures (CCT) across varying currents. Specifically, under a driving current of 20mA, the device incorporating RbKSiF6:1.2%Mn4+ exhibited a CRI of 94 and a CCT of 3732K, with a luminous efficacy of 61lm/W. These findings highlight the potential of green-synthesized RASFM phosphors in advancing the application of warm WLEDs.

Highly efficient AlGaN-based deep-ultraviolet light-emitting diodes: from bandgap engineering to device craft

AlGaN-based light-emitting diodes (LEDs) operating in the deep-ultraviolet (DUV) spectral range (210–280 nm) have demonstrated potential applications in physical sterilization. However, the poor external quantum efficiency (EQE) hinders further advances in the emission performance of AlGaN-based DUV LEDs. Here, we demonstrate the performance of 270-nm AlGaN-based DUV LEDs beyond the state-of-the-art by exploiting the innovative combination of bandgap engineering and device craft. By adopting tailored multiple quantum wells (MQWs), a reflective Al reflector, a low-optical-loss tunneling junction (TJ) and a dielectric SiO2 insertion structure (IS-SiO2), outstanding light output powers (LOPs) of 140.1 mW are achieved in our DUV LEDs at 850 mA. The EQEs of our DUV LEDs are 4.5 times greater than those of their conventional counterparts. This comprehensive approach overcomes the major difficulties commonly faced in the pursuit of high-performance AlGaN-based DUV LEDs, such as strong quantum-confined Stark effect (QCSE), severe optical absorption in the p-electrode/ohmic contact layer and poor transverse magnetic (TM)-polarized light extraction. Furthermore, the on-wafer electroluminescence characterization validated the scalability of our DUV LEDs to larger production scales. Our work is promising for the development of highly efficient AlGaN-based DUV LEDs.

Carbon Quantum Dots with Highly Efficient Bandgap Emission for Electroluminescent Light-Emitting Diodes

Carbon quantum dots (CQDs) feature bright and tunable photoluminescence, solution processability, and low toxicity, showing great potential in optoelectronics. The multicolor fluorescent CQDs were first fabricated as active layers in our lab, and then the high-performance electroluminescent warm white light-emitting diodes (LEDs) were obtained with the synthesized bright red CQDs. More significantly, through designing the triangular structure of the carbon core, fluorescent CQDs first achieved the narrow-bandwidth (∼30 nm) electroluminescent LEDs with appreciable stability, high color purity, and high luminescence performance. These results lay the foundation for the development of next-generation high performance displays based on CQDs. Here, we will report the large-scale synthesis of CQDs with near-unity photoluminescence quantum yield and 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. 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.References Yuxin Shi, Louzhen Fan, et al., Red Phosphorescent Carbon Quantum Dot Organic Framework-Based Electroluminescent Light-Emitting Diodes Exceeding 5% External Quantum Efficiency, Am. Chem. Soc. 2021, 143, 45, 18941–18951Ting Yuan, Louzhen Fan, et al., Carbon Quantum Dots with Near-Unity Quantum Yield Bandgap Emission for Electroluminescent Light-Emitting Diodes, Angew. Chem. Int. Ed. 2023, e202218568.Fanglong Yuan，Louzhen Fan, et al., Engineering triangular carbon quantum dots with unprecedented narrow bandwidth emission for multicolored LEDs, Nat. Commun., 2018, 9, 2249. Figure 1

High-performance sky-blue quasi-2D perovskite light-emitting diodes via synergistic defect passivation and phase narrowing strategies

Quasi-2D perovskite light-emitting diodes (PeLEDs) are considered as one of the most promising candidates for next-generation displays. Yet, the unstable electroluminescent spectra and inferior performance of blue PeLEDs hinder their commercial use. Herein, we demonstrate highly efficient quasi-2D pure bromide (QPB) sky-blue PeLEDs based on an oxygen-rich triethyl 2-acetylcitrate (TEAC) additive. The TEAC additive contains four C = O functional groups, offering several coordination sites to simultaneously passivate multiple bromine vacancy defects. Furthermore, it inhibits the growth of large n (n ≥ 5) phases to achieve narrow phases distribution. As a result, the TEAC-modified PeLEDs show sky-blue emission at 494 nm, with maximum current efficiency and external quantum efficiency up to 29.1 cd/A and 18.5 %, respectively. Moreover, the T50 lifetime of TEAC-modified PeLED is about 25 times higher than that of pristine PeLEDs. Our results provide a reliable approach to realizing high-efficiency blue quasi-2D PeLEDs.

Enhancing the performance of InGaN-based near-infrared light-emitting diodes under a weakly polarized electric field

This work presents a simulation analysis of nitride multi-quantum-well near-infrared light-emitting diodes (LEDs) with an emission wavelength of 1300 nm using Crosslight-APSYS software. The polarization electric field at the quantum wells was effectively tuned by adopting an Al0.02Ga0.19In0.79N quaternaries compound as the barrier for the In0.78GaN quantum wells, resulting in a near-zero polarization electric field. This approach significantly reduced band bending and increased the overlap of electron-hole wave functions within the quantum wells. Consequently, the internal quantum efficiency (IQE) in the nitride near-infrared LED improved, and the droop effect was significantly reduced. The Auger recombination mechanism that influences the droop effect was further analyzed. This provides an efficient approach for the development of high-performance InGaN-based near-infrared light-emitting diodes with high indium content.

High Stability and Corrosion-Resistant Gas of Recyclable and Versatile Manganese-Doped Lead-Free Double Perovskite Crystals toward Novel Functional Fabric and Photoelectric Device.

Lead-free halide perovskites possess excellent photoelectric properties, making them widely used in the photoelectric fields. Herein, lead-free double perovskite crystals (PCs) doped with manganese (Cs2NaInCl6:Mn2+) are successfully prepared by the more energy-efficient crystallization method. The crystals emit bright orange-red light under the ultraviolet (UV) lamp, showing unique optical properties. They have the highest photoluminescence quantum yield of 42.91%. The white light-emitting diodes (LEDs) are fabricated using these perovskite crystals, which show a color rendering index of 92 and external quantum efficiency (EQE) as high as 16.3%. Furtherly, perovskite-modified fiber paper made of aramid chopped fibers (ACFs) and polyphenylene sulfide (PPS) exhibited fluorescent properties under different conditions. This paper combines fiber composite technology with PPS fiber filter bags, which are widely used in environmental protection, for the first time and demonstrates functional fiber filter bags with fluorescent characteristics. This filter bag provides an idea for the automatic detection of industrial filtration. Meanwhile, after being exposed to industrial waste gas for 60h, the filter bag can maintain superior fluorescence performance. In this study, lead-free double perovskites are synthesized using an efficient method for preparing high-performance LEDs and high-stability fluorescent fibers. Concurrently, the application of perovskites in environmental protection is expanded.

Drag force shear manipulating ligand distribution at perovskite buried interface enables efficiently suppressed EQE roll-off of perovskite light-emitting diodes

Effectively manipulating the ligand distribution at the perovskite buried interface is critical for achieving high-performance nanocrystal-based perovskite light-emitting diodes (PeLEDs). However, it is challenging to realize it due to the non-exposed feature of the buried interface. Here, the drag force shear (DFS) is utilized to successfully regulate the ligand distribution at the perovskite buried interface which can effectively suppress the EQE roll-off of devices. By manipulating the ligand distribution at the perovskite buried interface, it is revealed that a more ligand preservation could result in an improved defect passivation leading to higher EQE, while the carrier injection barrier is increased simultaneously making devices suffer from severe EQE roll-off and decreased luminance, and vice versa. With the help of optimizing the ligand distribution by manipulating the DFS, the balance between carrier injection and interfacial defect passivation is successfully achieved. Resultantly, an enhanced EQE of 17.24 % with substantially suppressed EQE roll-off is reached, culminating in a remarkable luminance of 61,900 cd/m2. This work presents an efficient approach to control ligand distribution at the perovskite buried interface and offers valuable insights for realizing high luminance and low EQE roll-off of PeLEDs.

Efficient Perovskite Nanograin Light-Emitting Diodes in Green-to-Blue Gamut with Co-Additive Engineering.

Perovskite nanograins exceeding the Bohr exciton diameter show great potential for high-performance light-emitting diodes (LEDs) owing to their bandgap homogeneity, spatial charge confinement, and nonlocal interaction. However, it is challenging to directly synthesize proper nanograins along with reduced crystal defects on functional substrate, and the corresponding high-efficiency perovskite LEDs (PeLEDs) have rarely been reported. In this study, crystallization modulation for perovskites with an effective co-additive system, including lithium bromide, p-fluorophenethylammonium bromide, and 18-crown-6, is performed. Furthermore, it is demonstrated that the proposed co-additive system can synergistically retard perovskite crystallization and reduce crystal defects. Consequently, high-quality perovskite nanograin solids (≈22.8nm) are obtained with a high photoluminescence quantum yield (≈88%). These superior optical properties contribute to developing efficient green PeLEDs with a champion external quantum efficiency (EQE) of 28.4% and an average EQE of 27.1%. The co-additive system can be universally applied to mixed-halide perovskite nanograin LED, presenting a maximum EQE of 24.4%, 21.6%, 17.5%, and 11.1% for the blue device at 496, 488, 478, and 472nm, respectively, along with a narrow spectral linewidth (17-14nm) and stable color. These results supplement the research on high-efficiency perovskite nanograin LEDs for multicolor displays and lighting.

Stabilized CsPbBr3 quantum dots in flower-like LYH matrix for high-performance white light-emitting diodes

Stabilized CsPbBr3 quantum dots in flower-like LYH matrix for high-performance white light-emitting diodes

Well-type thick-shell quantum dots combined with double hole transport layers device structure assisted realization of high-performance quantum dot light-emitting diodes

Quantum dot (QD) light-emitting diodes (QLEDs) are promising for next-generation lighting and displays. Considering the optimization design of both the QD and device structure is expected to improve the QLED's performance significantly but has rarely been reported. Here, we use the thick-shell QDs combined with a dual-hole transport layer device structure to construct a high-efficiency QLED. The optimized thick-shell QDs with CdS/CdSe/CdS/ZnS seed/spherical quantum well/shell/shell geometry exhibit a high photoluminescence quantum yield of 96% at a shell thickness of 5.9 nm. The intermediate emissive CdSe layer with coherent strain ensures defect-free growth of the thick CdS and ZnS outer shells. Based on the orthogonal solvents assisted Poly-TPD&PVK dual-hole transport layer device architecture, the champion QLED achieved a maximum external quantum efficiency of 22.5% and a maximum luminance of 259955 cd m-2, which are 1.6 and 3.7 times that of thin-shell QDs based devices with single hole transport layer, respectively. Our study provides a feasible idea for further improving the performance of QLED devices.

Embedding Te4+ into Sn4+-Based Metal Halide To Passivate Structure Defects for High-Performance Light-Emitting Application.

Low-dimensional lead-halide hybrids are an emerging class of optical functional material but suffer the problems of toxicity and poor air stability. Among lead-free metal halides, tin(IV)-based metal halides are promising optoelectronic materials due to their robust structure and environmental friendliness. However, their photoluminescence (PL) properties are poor, and the underlying mechanisms are still elusive. Herein, a stable Sn4+-based halide hybrid, (C4H7N2)2SnCl6, was developed, which however exhibits poor PL properties at room temperature (RT) due to the lattice defects and the robust crystal structure. To enhance its PL efficiency, the Te4+ ion with a stereoactive 5s2 lone pair has been introduced into the lattice. As a result, Te4+-doped (C4H7N2)2SnCl6 displays broadband orange emission (∼640 nm) with a PL efficiency of ∼46% at RT. Interestingly, Te4+-doped (C4H7N2)2SnCl6 shows triple emission bands at 80 K, which could be due to the synergistic effect of the organic cations and the self-trapped state induced by Te4+. Additionally, high-performance white light-emitting diodes were prepared using Te4+-doped (C4H7N2)2SnCl6, revealing the potential of this material for lighting applications. This study provides new insight into the PL mechanism of Sn4+-based metal-halide hybrids and thus facilitates the design and development of eco-friendly light-emitting metal halides.

Layer-controllable synthesis, lattice structural Determination, and fluorescence lifetime imaging of (HA)2(MA)n-1PbnI3n+1 Quasi-2D organic-inorganic perovskite microsheets

Hybrid quasi-two-dimensional (quasi-2D) perovskites have attracted great interest due to their excellent photovoltaic and light-emitting properties, which enable the rapid development of high-performance perovskite-based solar cells, light-emitting diodes, and lasers. Although many efforts have been made to improve the quality and stability of organic-inorganic perovskites, the controlled synthesis of high-quality layered perovskites remains challenging. Here, single-crystalline quasi-2D (HA)2(MA)n-1PbnI3n+1 perovskites with layer numbers of n from 1 to 3 have been synthesized in a controllable manner, exhibiting stable lattice structures and tunable optical emission. Structurally, hexylamine (HA) with longer alkyl chains was used as an organic spacer in Ruddlesden-Popper (RP) phase perovskites to improve the chemical stability of perovskites. Various ratios of precursor materials were adopted for separating pure and large-scale quasi-2D (HA)2(MA)n-1PbnI3n+1 perovskites, in which different layer-number perovskites with tunable band gaps were obtained with the modulated fluorescence lifetimes. Our lattice structural and fluorescence-lifetime characterizations of RP-phase perovskites provide critical information on the emerging quasi-2D perovskite-crystal systems and their fluorescence relaxation dynamics. The employed strategy to synthesize high-quality perovskites (HA)2(MA)n-1PbnI3n+1 is technically essential to develop the rising perovskite-based photovoltaic and light-emitting applications.

Zwitterionic additive for high-performance pure-blue perovskite light-emitting diodes

Zwitterionic additive for high-performance pure-blue perovskite light-emitting diodes

Spray pyrolysis–deposited NiO film as a hole-injection layer for CsPbBr3 nanocrystal-based light-emitting diodes

In perovskite-based light-emitting diodes (LEDs), employing an inorganic material for the hole-injection layer instead of an organic material is crucial for attaining optimal performance and device stability. This layer needs to exhibit [Formula: see text] -type conductivity with high carrier mobility while being fabricated with a simple and industrially compatible method. In this study, uniform and thin [Formula: see text] -type NiO films were deposited through spray pyrolysis in an air atmosphere. The as-deposited film showed poor crystallinity, and high resistance reduced hole-injection performance. Subsequent thermal treatment at 500∘C enhanced the crystallinity of the layer, reducing resistance and improving LED performance. The film exhibited [Formula: see text] -type semiconductor characteristics, and its carrier mobility, carrier concentration and resistivity were 53.0 × [Formula: see text]cm3, 116cm2⋅ [Formula: see text] and 0.98[Formula: see text] ⋅ [Formula: see text], respectively. Moreover, a compact [Formula: see text] nanocrystal (NC) film as an emitting layer was deposited with a centrifugal coating technique. The resulting LED component featuring a fluoride-doped tin oxide (FTO)/NiO/[Formula: see text] NCs/tris-(1-phenyl-1H-benzimidazole)/LiF/Au structure and demonstrating high luminance, current efficiency and external quantum efficiency (EQE) reached 12,000 cd⋅[Formula: see text], 8.8 cd ⋅ [Formula: see text] and 3.56%, respectively, at 5.5 V. Our work offers a simple and unique approach for accelerating the development of advanced interfacial materials and circumventing major interfacial problems in solution-processed perovskite NC films for high-performance LEDs.

Direct Evidence of the Effect of Water Molecules Position in the Spectroscopy, Dynamics, and Lighting Performance of an Eco-Friendly Mn-Based Organic-Inorganic Metal Halide Material for High-Performance LEDs and Solvent Vapor Sensing.

Luminescent Mn(II)-based organic-inorganic hybrid halides have drawn attention as potential materials for sensing and photonics applications. Here, the synthesis and characterization of methylammonium (MA) manganese bromide ((MA)nBrxMn(H2O)2, (n = 1, 4 and x = 3, 6)) with different stoichiometries of the organic cation and inorganic counterpart, are reported. While the Mn2+ centers have an octahedral conformation, the two coordinating water molecules are found either in cis (1) or in trans (2) positions. The photophysical behavior of 1 reflects the luminescence of Mn2+ in an octahedral environment. Although Mn2+ in 2 also has octahedral coordination, at room temperature dual emission bands at ≈530 and ≈660nm are observed, explained in terms of emission from Mn2+in tetragonally compressed octahedra and self-trapped excitons (STEs), respectively. Above the room temperature, 2 shows quasi-tetrahedral behavior with intense green emission, while at temperatures below 140K, another STE band emerges at 570nm. Time-resolved experiments (77-360K) provide a clear picture of the excited dynamics. 2 shows rising components due to STEs formation equilibrated at room temperature with their precursors. Finally, the potential of these materials for the fabrication of color-tunable down-converted light-emitting diode (LED) and for detecting polar solvent vapors is shown.

Energy Transfer-Dominated Quasi-2D Blue Perovskite Light-Emitting Diodes.

The bromide-chloride mixed quasi-two-dimensional (2D) perovskite, with a natural quantum well structure and tunable exciton binding energy, has gained significant attention for high-performance blue perovskite light-emitting diodes (PeLEDs). However, the relative importance of having a low trap state density or efficient exciton transfer for high-efficiency electroluminescence (EL) performance remains elusive. Here, two molecules with the benzoic acid group, sodium 4-fluorobenzoate (SFB) and 3,5-dibromobenzoic acid (DBA), are used to modulate the phase distribution and trap state to explore the effect between energy transfer and defect passivation. As a result, when the n = 1 phase is inhibited in both films, the DBA@SFB-modified perovskite films achieve a higher photoluminescence quantum yield (PLQY) than the SFB-modified perovskite films due to effective defect passivation. However, DBA@SFB-modified PeLEDs exhibit lower external quantum efficiency (EQE) compared to SFB-modified PeLEDs due to the poor exciton transfer between the low-dimensional phase. This demonstrates that passivation strategies may enhance photoluminescence through reducing nonradiative recombination, but the effect of phase distribution is pivotal for EL performance by efficient energy transfer in quasi-2D perovskites. Femtosecond time-resolved transient absorption measurements confirm the fastest carrier dynamics in SFB-modified perovskite films, further corroborating the above result. This work provides useful information about phase modulation and defect passivation for high-efficiency blue quasi-2D PeLEDs.

Nanosurface-reconstructed perovskite for highly efficient and stable active-matrix light-emitting diode display.

Perovskite quantum dots (QDs) are promising for various photonic applications due to their high colour purity, tunable optoelectronic properties and excellent solution processability. Surface features impact their optoelectronic properties, and surface defects remain a major obstacle to progress. Here we develop a strategy utilizing diisooctylphosphinic acid-mediated synthesis combined with hydriodic acid-etching-driven nanosurface reconstruction to stabilize CsPbI3 QDs. Diisooctylphosphinic acid strongly adsorbs to the QDs and increases the formation energy of halide vacancies, enabling nanosurface reconstruction. The QD film with nanosurface reconstruction shows enhanced phase stability, improved photoluminescence endurance under thermal stress and electric field conditions, and a higher activation energy for ion migration. Consequently, we demonstrate perovskite light-emitting diodes (LEDs) that feature an electroluminescence peak at 644 nm. These LEDs achieve an external quantum efficiency of 28.5% and an operational half-lifetime surpassing 30 h at an initial luminance of 100 cd m-2, marking a tenfold improvement over previously published studies. The integration of these high-performance LEDs with specifically designed thin-film transistor circuits enables the demonstration of solution-processed active-matrix perovskite displays that show a peak external quantum efficiency of 23.6% at a display brightness of 300 cd m-2. This work showcases nanosurface reconstruction as a pivotal pathway towards high-performance QD-based optoelectronic devices.

Retrograde Solubility of Methylammonium Lead Iodide in γ-Butyrolactone Does Not Enhance the Uniformity of Continuously Coated Films.

Halide perovskite thin films can be the centerpiece of high-performance solar cells, light-emitting diodes, and other optoelectronic devices if the films are of high uniformity and relatively free of pinholes and other defects. A common strategy to form dense films from solution has been to generate a high density of nuclei by rapidly increasing supersaturation, for example, by timely application of an antisolvent or forced convection. In this work, we examine the role of retrograde solubility, wherein solubility decreases with increasing temperature, as a means of increasing the nucleation density and film coverage of slot-die-coated methylammonium lead iodide (MAPbI3) from γ-butyrolactone (GBL) solution. Coverage was investigated as a function of the substrate temperature and the presence and temperature of an air knife. Results were considered within the framework of the dimensionless modified Biot number, which quantifies the interplay between evaporation and horizontal diffusion. Moderate temperatures and a heated air knife improved film coverage and morphology by enhanced nucleation up to ∼80 °C. However, despite the dense nucleation enabled by retrograde solubility, slow evaporation as a result of the low vapor pressure of GBL, combined with Ostwald ripening at high temperatures, prevented the deposition of void-free, device-quality films. This work has provided a more detailed understanding of the interplay between perovskite processing, solvent parameters, and film morphology and ultimately indicates the obstacles to forming dense, uniform films from solvents with high boiling points even in the presence of rapid nucleation.

Onion-like multicolor thermally activated delayed fluorescent carbon quantum dots for efficient electroluminescent light-emitting diodes

Carbon quantum dots are emerging as promising nanomaterials for next-generation displays. The elaborate structural design is crucial for achieving thermally activated delayed fluorescence, particularly for improving external quantum efficiency of electroluminescent light-emitting diodes. Here, we report the synthesis of onion-like multicolor thermally activated delayed fluorescence carbon quantum dots with quantum yields of 42.3–61.0%. Structural, spectroscopic characterization and computational studies reveal that onion-like structures assembled from monomer carbon quantum dots of different sizes account for the decreased singlet-triplet energy gap, thereby achieving efficient multicolor thermally activated delayed fluorescence. The devices exhibit maximum luminances of 3785–7550 cd m−2 and maximum external quantum efficiency of 6.0–9.9%. Importantly, owing to the weak van der Waals interactions and adequate solution processability, flexible devices with a maximum luminance of 2554 cd m−2 are realized. These findings facilitate the development of high-performance carbon quantum dots-based electroluminescent light-emitting diodes that are promising for practical applications.