Application In Light-emitting Diodes Research Articles

Photoluminescence Blinking of Quantum Confined CsPbBr3 Perovskite Nanocrystals: Influence of Size

Quantum confined CsPbBr3 nanocrystals (NCs) with adjustable photoluminescence (PL) in the range of 470–500 nm are particularly desirable for applications in light-emitting diodes and many quantum technologies. Exploration of the full potential of these perovskite NCs requires an understanding of the random fluctuation of their PL at the single-particle level, commonly termed as blinking. In this work, we study the PL blinking of quantum confined single NCs of CsPbBr3 of three different sizes between 3.80 and 5.90 nm in immobilized and fluid conditions to understand the recombination pathways and dynamics of the photogenerated charge carriers. In the immobilized state, the PL intensity trajectories and PL lifetime-intensity distributions of these single NCs reveal the contributions of both Auger recombination and trapping of hot carriers to the PL fluctuation. The results suggest a higher carrier trapping rate constant for smaller NCs. The fluorescence correlation spectroscopy and fluorescence lifetime correlation spectroscopy measurements on freely diffusing NCs show a higher off-state fraction and lower per-particle brightness of the smaller NCs. It is concluded that a larger trap depth and higher probability density of the carriers at the surface in smaller NCs make the trapping process more feasible and detrapping more difficult. The results provide first information on the effect of size on PL blinking of the quantum confined CsPbBr3 NCs, and this knowledge is expected to be useful in better designing photoluminescent samples of this class for optoelectronic applications.

Top-Emitting Quantum Dot Light-Emitting Diodes: Theory, Optimization, and Application.

The superior optical properties of colloidal quantum dots (QDs) have garnered significant broad interest from academia and industry owing to their successful application in self-emitting QD-based light-emitting diodes (QLEDs). In particular, active research is being conducted on QLEDs with top-emission device architectures (TQLEDs) owing to their advantages such as easy integration with conventional backplanes, high color purity, and excellent light extraction. However, due to the complicated optical phenomena and their highly sensitive optoelectrical properties to experimental variations, TQLEDs cannot be optimized easily for practical use. This review summarizes previous studies that have investigated top-emitting device structures and discusses ways to advance the performance of TQLEDs. First, theories relevant to the optoelectrical properties of TQLEDs are introduced. Second, advancements in device optimization are presented, where the underlying theories for each are considered. Finally, multilateral strategies for TQLEDs to enable their wider application to advanced industries are discussed. This work believes that this review can provide valuable insights for realizing commercial TQLEDs applicable to a broad range of applications.

Tunable photoluminescence of Ba2GdF7: Tb3+, Eu3+ nanoparticles based on energy transfer

Tb3+, Eu3+ singly doped and Tb3+-Eu3+ co-doped Ba2GdF7 nanoparticles were obtained by one-step hydrothermal process. Under 273 or 368 nm ultraviolet (UV) excitation, by changing the ratio of Tb3+ and Eu3+, the emission color of Ba2GdF7: Tb3+, Eu3+ are manipulated from green to yellow, orange and red based on energy transfer (ET) from Gd3+ to Tb3+, Eu3+ and from Tb3+ to Eu3+. The ET mechanism among Tb3+ and Eu3+ was determined as dipole-dipole interaction by the lifetime change of Tb3+. The thermal stability of Ba2GdF7: 40%Tb3+, 3%Eu3+ phosphor was studied and the activation energy was calculated to be 0.289 eV at 273 nm and 0.297 eV at 368 nm excitation. The multi-color emitting Ba2GdF7: Tb3+, Eu3+ nanophosphors might have a promising application in phosphors-converted light-emitting diodes.

Cation-Disorder-Enhanced Unintentional Doping in MgSnN2

${\mathrm{Mg}\mathrm{Sn}\mathrm{N}}_{2}$ has recently attracted significant interest as a promising candidate for applications in green light-emitting diodes and photovoltaic absorbers. However, the experimentally synthesized ${\mathrm{Mg}\mathrm{Sn}\mathrm{N}}_{2}$ samples suffer from a high concentration of unintentionally doped electrons, and their origin is not fully understood yet. By performing first-principles calculations, we investigate the properties of intrinsic point defects and oxygen impurities in cation-ordered and -disordered wurtzite ${\mathrm{Mg}\mathrm{Sn}\mathrm{N}}_{2}$. It is found that the cation antisite defect ${\mathrm{Sn}}_{\mathrm{Mg}}$ is the predominant donor defect, contributing an electron concentration as high as ${10}^{17}\phantom{\rule{0.25em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ to cation-ordered ${\mathrm{Mg}\mathrm{Sn}\mathrm{N}}_{2}$. However, this value is 2--3 orders of magnitude lower than experimental observations (${10}^{19}\ensuremath{-}{10}^{20}\phantom{\rule{0.25em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$). We further show that cation disorder significantly decreases the formation energies of defects, leading to a much higher electron concentration (${10}^{19}\phantom{\rule{0.25em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$) than in the case of the cation-ordered phase. The reduced formation energy can be understood by the energy gain due to the creation of energetically favorable local motif structures after the formation of defects. Hence, reducing the degree of cation disorder is beneficial for decreasing the densities of defects and self-doped carriers.

Evolution of Frenkel defect pairs in β-Ga2O3 thin film with the introduction of oxygen and its application in GaN-based ultraviolet light-emitting diode

In this work, β-Ga2O3 thin films were deposited by radio frequency (RF) magnetron sputtering technique. The effect of oxygen-argon flow ratio (OAFR) on the formation of Frenkel defect pairs was systematically analyzed. The Frenkel defect pairs would become abundant when the OAFR was 25:25 sccm, resulting in a severe damage in crystalline quality and an increase in the density of disorder. With the further increase of OAFR, Frenkel defect pairs would dramatically decrease or even vanish due to the significant reduction of oxygen vacancies (V0). Immediately after that, on the basis of avoiding the influence of Frenkel defect pairs inside the β-Ga2O3 films to the devices, the p-NiO/i-Ga2O3/n-GaN diode was fabricated from the as-prepared high-quality β-Ga2O3 film after post-deposition annealing as the electron-blocking layer. Subsequently, its electrical characteristics were investigated in detail which exhibited excellent rectification characteristics under all test temperatures. Correspondingly, the device achieved electroluminescence (EL) with a dominant sharp emission peak in the ultraviolet range (∼375 nm). In the end, the energy band diagram was used for in-depth analysis of the EL mechanism.

Tunable and Efficient Photoluminescence of Lanthanide-Doped Cs2NaScCl6 Double Perovskite Single Crystals toward Multifunctional Light-Emitting Diode Applications.

Lead-free halide double perovskite, as one of the promising candidates for lead halide perovskite materials, shows great potential in light-emitting diodes (LEDs), benefiting from its environmental friendliness and high chemical stability. However, the poor regulation of the emission spectra severely limits its application range. Herein, various lanthanide ions were successfully doped in Cs2NaScCl6 double perovskite single crystals (DPSCs) to yield effective and stable emissions spanning from visible to near-infrared (NIR) regions. Notably, efficient energy transfer from the host to the dopants enables tunable emissions with good chromaticity, which is rarely reported in the field of lead-free double perovskite. Moreover, density functional theory calculations reveal that the high local electron density around the [LnCl6]3- octahedron in DPSCs plays a key role in the improvement of photoluminescence quantum yields (PLQYs). The optimal PLQYs are up to 84%, which increases around 3 times over that of the undoped sample. Finally, multicolor and NIR LEDs based on Ln3+-doped Cs2NaScCl6 DPSCs were fabricated and had different application functions. Specifically, the single-composite white LED shows adjustable coordinates and correlated color temperatures, while the NIR LED shows good night vision imaging. This work provides new inspiration for the application of efficient multifunctional LEDs based on lead-free double perovskite materials.

GeSn/Ge Multiquantum-Well Vertical-Cavity Surface-Emitting p-i-n Structures and Diode Emitters on a 200 mm Ge-on-Insulator Platform

An efficient monolithically integrated light source with complementary metal-oxide-semiconductor (CMOS) compatibility remains the missing component to enable Si photonics for various applications. In particular, vertical-cavity-surface-emitting (VCSE) light sources, such as resonant cavity light-emitting diodes (RCLEDs) and vertical-cavity surface-emitting lasers (VCSELs), are strong contenders due to their compact size, circular emission profile with low beam divergence, wafer-scale fabrication compatibility, high bandwidth, and high coupling efficiency to fiber optic cables. We report the first demonstration of 8-in. wafer-scale GeSn/Ge multiple-quantum-well VCSE p-i-n structures and diodes for laser or light-emitting diode (LED) applications in Si photonics by wafer bonding and layer transfer techniques, which are challenging for all-epitaxy routes. The wafer could be 12 in. (300 mm) since the MQW gain medium is grown on a 300 mm Si wafer, and the bonding is wafer-scale. Alternative dielectric layers (SiO2/SiN/SiO2), introduced by wafer bonding, under the emitting structure, serve as the bottom mirror for the vertical cavity. The Ge0.92Sn0.08/Ge MQW layer is utilized to improve the material quality and to confine injected carriers. As a result, more than 8× enhancement of light emission due to the vertical cavity resonance was demonstrated by photoluminescence spectroscopy. Besides, the spectral purity is enhanced by the single-longitudinal-mode cavity. The intensity of light emission is insensitive to the temperature range from 4 to 300 K and even becomes stronger at higher temperatures since the stronger resonant cavity effect at higher temperatures compensates for the drop in light emission efficiency caused by nonradiative centers. The vertical cavity effect on the light emission is further verified by reflectivity spectroscopy and optical simulations. A positive gain can be achieved as indicated by optical gain calculations. Room-temperature electroluminescence and an excellent carrier injection efficiency of the MQW VCSE diode are observed, showing its potential for electrically injected RCLEDs and VCSELs.

Dual-function ligand surface control to achieve high efficiency and brightness perovskite quantum dots LED devices

Metal halide perovskite quantum dots (QDs) have significant potential for application in light-emitting diodes (LED) owing to their superior optical properties. However, the dynamic instability of traditional oleic acid/amine ligands has a considerable impact on the optical and chemical properties of the surface. Additionally, one of its insulating qualities restricts the practical application of electroluminescent devices. In this case, the dual-function ligand DDA-MeS can passivate surface defects while also stabilizing chelation on QDs surface. As a result, the electrical performance of green QDs-LED devices is greatly enhanced, the external quantum efficiency is raised to 10.18%, the maximum brightness is also boosted to 8025 cd/m2, and the turn-on voltage is decreased to 2.5 V. This work also provides a novel strategy for the development of green LED devices with dual-function ligands that can be highly effective and bright.

Effect of donor/acceptor on the charge transfer and exciton harvest of pyrene-phenanthroimidazole dyads

Designing blue emitters with polyaromatic hydrocarbons such as anthracene and pyrene is more challenging as their derivatives are prone for aggregation caused emission quenching. We report herein three new pyrene-based deep blue emitting materials containing phenanthroimidazole moiety and a diphenylamine donor or cyano acceptor. Though the absorption of the compounds is similar, the emission were altered by the peripheral unit, due to the modulation in the donor-acceptor interaction and the intramolecular charge transfer (CT) in the excited state. The solvatochromic emission data indicated the presence of hybridized local and CT excited state for the parent core and its diphenylamine derivative. However, the cyano derivative inherits more CT characteristics. Additionally, all the dyes were found to exhibit acidochromism due to the facile interaction of phenanthroimidazole moiety with the acid. All the dyes were used for organic light-emitting diodes (OLED) applications with tris(4-carbazoyl-9-ylphenyl)amine (TCTA) host material, which exhibited deep blue or cyan-blue color electroluminescence with high external quantum efficiency. The device consisting of a dye with parent core as a dopant in TCTA host exhibited highest external quantum efficiency (EQE) of 7.5% with current efficiency 3.3 cd/A and luminance 2734 cd/m2 attributable to the effective utilization of excitons harvested through the HLCT channel.

Photocatalytic oxidation of volatile organic compounds (VOCs) in air using ultraviolet light-emitting diodes (UV-LEDs)

The aim of this study was to experimentally investigate the application of ultraviolet light-emitting diodes (UV-LEDs) for removing volatile organic compounds (VOCs) from air. For this purpose, a 365 nm UV-LED and a photocatalyst were used in a batch reactor to study the photocatalysis of toluene as the representative pollutant. It was demonstrated that combining reduced graphene oxide (rGO) with titanium dioxide (TiO2) and immobilizing the catalyst on the porous substrate could significantly improve the photocatalytic activity compared with the pristine TiO2 catalyst on a solid substrate. Photocatalyst deactivation was also studied by running cyclical tests. The photocatalytic crystal structure remained intact, but catalytic activity declined more than 80% after five consecutive photocatalytic tests for treating relatively high toluene concentrations. The adsorbed intermediates of toluene photocatalysis, such as benzoic acid, benzaldehyde, and benzyl alcohol, were identified, and the deactivation mechanism was proposed. It was shown that the deactivated photocatalyst can be effectively regenerated by UV-LED irradiation of 38.5 mW/cm2 irradiance within two hours. Overall, it was concluded that the UV-LED with a TiO2 on porous support provides an effective method for practical air purification applications.

High luminous efficiency of a phosphor-in-glass plate by optimization of the glass and phosphor content for high-power LED applications

Generally, white light-emitting diodes (LEDs) are fabricated by combining blue LED chips with yellow phosphors. When fabricating white LEDs, the phosphor is typically mixed with an organic resin and applied to the LED chips as a paste. A phosphor-in-glass (PiG) plate can alternatively be used to address the poor high-temperature reliability of the paste method. However, because pores form in the PiG plate during the sintering process, this method results in a loss of optical efficiency. Accordingly, we aimed to improve the fluidity of glass and light efficiency by optimizing the sintering temperature of the glass powder and the phosphor content respectively for reducing internal porosity in the PiG. In this study, glass powder was sintered at different temperatures to produce glass plates, while also varying the phosphor content to fabricate PiG plates. The optimal light characteristics were realized with a glass sintering temperature of 640 °C and a phosphor content of 20 wt%.

A cyanostilbene derivative containing –CF3: Synthesis and applications in sensors, information rewritable, encryption and LED

An organic small molecule fluorescent material α-cyanostilbene derivative (2) containing trifluoromethyl (electron acceptor) and dimethylamino (electron donor) has been designed and synthesized by a simple two-step reaction and mild conditions. The structure of target product 2 was characterized using elemental analysis, FT-IR and NMR (1H, 13C, 19F) methods. Compound 2 has strong luminescence in solution and solid states (i.e., dual-state emission, DSE) and aggregation-induced enhanced emission, (AIEE) effect. 2 can be used to recognition the polarity of solvents by “naked eye” under a UV lamp or by fluorescence spectrometer because of its obvious solvatochromic behaviour. 2 can be applied in information rewritable storage, encryption and acid/base sensor, owing to its colour and emission wavelength/intensity can be switched under grinding and acid/base stimulation. The acid/base titration 1H NMR spectra of 2 prove that acidichromism results from the conversion of protonation (2-H+)/deprotonation (2). The results of powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) confirm that the mechanochromic is caused by the morphological transition of 2. Moreover, 2 can be used in light emitting diode (LED) due to its desirable solid-state luminescence performance.

Room Temperature Phosphorescence Carbon Dots: Preparations, Regulations, and Applications.

Room temperature phosphorescence (RTP) materials have drawn considerable attention by virtue of their outstanding features. Compared with organometallic complexes and pure organic compounds, carbon dots (CDs) have emerged as a new type of RTP materials, which show great advantages, such as moderate reaction condition, low toxicity, low cost, and tunable optical properties. In this review, the important progress made in RTP CDs is summarized, with an emphasis on the latest developments. The synthetic strategies of RTP CDs will be comprehensively summarized, followed by detailed introduction of their performance regulation and potential applications in anti-counterfeiting, information encryption, sensing, light-emitting diodes, and biomedicine. Finally, the remaining major challenges for RTP CDs are discussed and new opportunities in the future are proposed.

Dual‐Defect Manipulation Enables Efficient and Spectrally Stable Blue Perovskite Light‐Emitting Diodes

AbstractPerformance of blue solution‐processed perovskite light‐emitting diodes (LEDs) is limited by availability of blue perovskite materials. Herein, 4‐(trifluoromethyl)benzoyl ammonium bromide (4‐TMBABr) is used with abundant NH and CO groups to passivate the defects and produce highly stable PEAxPA2‐x(CsPbBr3)n‐1PbBr4 perovskites for blue LED applications. The NH group in the 4‐TMBABr suppresses the Br‐ion mismatch through hydrogen bonds (N‐H···Br) and CO group coordinates the unsaturated lead dangling bonds (CO:Pb). The effective defect passivation by 4‐TMBABr reduces the nonradiative recombination in the perovskite films, hence enhancing its optical performance. In the LED structure, the sodium bis(trifluoromethanesulfonyl)imide (SBTI) modified NiOx films are used to improve the hole transport and to inhibit the fluorescence quenching of the perovskite layer. The dual‐defect manipulation strategy is advantageous for producing efficient and spectrally stable blue perovskite LEDs, and the authors demonstrate an LED with maximum luminance of 1094 cd m−2 and external quantum efficiency of 10.3%. This work can inform and underpin future development of blue perovskite LEDs with highly efficient and stabile performance.

Constructing high-efficiency aggregation-induced delayed fluorescence molecules and OLEDs applying C-H···N hydrogen bond manipulation strategy

Thermally activated delayed fluorescent materials with aggregation-induced emission (AIE) feature have shown great potential applications in organic light-emitting diodes (OLEDs). In this work, three donor-acceptor molecules including PM-DMSFAC, Trz-DMSFAC, and PYPM-DMSFAC were constructed using dimethyl spiro-fluorene acridine as electron donor, while pyrimidine, triazine, and pyrimidine-pyridine hybrid groups with multiple C–H···N hydrogen bonds were respectively chosen as the acceptor units. There is a large dihedral angle between donor and acceptor, which facilitates the three molecules with efficient reverse intersystem crossing, and meanwhile the large steric hindrance endows them with AIE property. In comparison with PM-DMSFAC, an extra nitrogen atom is added in Trz-DMSFAC and PYPM-DMSFAC, making them more electronegative and exhibiting more intramolecular and intermolecular C–H···N interactions, which result in more stable molecular structures and higher PLQYs. When adopted to construct OLEDs, Trz-DMSFAC and PYPM-DMSFAC devices exhibit significantly improved efficiency. Importantly, Trz-DMSFAC afforded the best device performances with a maximum external quantum efficiency of 21.7% for non-doped OLED and 32.6% for doped device.

Intermolecular arrangement facilitated broadband blue emission in group-12 metal (Zn, Cd) hybrid halides and their applications

Various fluorescent organic materials are widely known for their potential applications in light-emitting diodes, organic lasers, anti-counterfeiting and bio-imaging. However, poor emission efficiency and stability issues limit their usability. Here we report the syntheses, crystal and electronic structures, and optical characterizations of two new hybrid organic-inorganic group 12 halides, (P-xd)ZnCl4 and (P-xd)CdCl4 (where (P-xd) = p-xylylenediammonium). Single crystals of both compounds can be conveniently synthesized by solution chemistry methods from their low-cost, low toxicity and easily available precursors. (P-xd)ZnCl4 possesses a crystal structure featuring alternating layers of organic cations and completely separated anionic [ZnCl4]2- tetrahedral units of zero-dimensional (0D) connectivity. In contrast, (P-xd)CdCl4 adopts similar layering of organic cations sandwiched between perovskite sheets of two-dimensional (2D) connectivity, which are formed by corner-sharing anionic [CdCl6]4- octahedral units. The structural, optical, and electronic studies suggest that the incorporation of organic and inorganic structural units into a hybrid structure improves its blue emission efficiency with nearly 23 times and 4 times higher photoluminescence quantum yield (PLQY) values in (P-xd)ZnCl4 and (P-xd)CdCl4, respectively, as compared to the organic precursor. Notably, PLQY of 23% for (P-xd)ZnCl4 is the highest reported to date for Zn-based hybrid organic-inorganic metal halides, where emission originates from the organic component. Both (P-xd)ZnCl4 and (P-xd)CdCl4 demonstrate considerably improved air-, thermal- and photostability, which suggest their suitability for potential practical applications such as fingerprint detection and solid-state lighting.

Self-powered perovskite photon-counting detectors.

Metal-halide perovskites (MHPs) have been successfully exploited for converting photons to charges or vice versa in applications of solar cells, light-emitting diodes and solar fuels1-3, for which all these applications involve strong light. Here we show that self-powered polycrystalline perovskite photodetectors can rival the commercial silicon photomultipliers (SiPMs) for photon counting. The photon-counting capability of perovskite photon-counting detectors (PCDs) is mainly determined by shallow traps, despite that deep traps also limit charge-collection efficiency. Two shallow traps with energy depth of 5.8 ± 0.8 millielectronvolts (meV) and 57.2 ± 0.1 meV are identified in polycrystalline methylammonium lead triiodide, which mainly stay at grain boundaries and the surface, respectively. We show that these shallow traps can be reduced by grain-size enhancement and surface passivation using diphenyl sulfide, respectively. It greatly suppresses dark count rate (DCR) from >20,000 counts per second per square millimetre (cps mm-2) to 2 cps mm-2 at room temperature, enabling much better response to weak light than SiPMs. The perovskite PCDs can collect γ-ray spectra with better energy resolution than SiPMs and maintain performance at high temperatures up to 85 °C. The zero-bias operation of perovskite detectors enables no drift of noise and detection property. This study opens a new application of photon counting for perovskites that uses their unique defect properties.

Precisely Slight Regulation of Emission Maxima and Construction of Highly Efficient Electroluminescent Materials with High Color Purity.

Advanced multiple resonance induced thermally activated delayed fluorescence (MR-TADF) emitters have emerged as a privileged motif for applications in organic light-emitting diodes (OLEDs), because they furnish highly tunable bandgap with emission ranges spanning the visible light region, and have the intrinsic properties of outstanding TADF characteristics and high color purity emission. One of the typical construction paradigms of MR-TADF molecule is based on polycyclization of MR parent core and a representative target model molecule BN-TP has been prepared. Herein, based on the unique nitrogen-atom embedding molecular engineering (NEME) strategy, a series of congeners of BN-TP, namely BN-TP-Nx (x = 1, 2, 3, 4), have been customized. The nitrogen-atom anchored at different position of triphenylene hexagonal lattice entails varying degrees of perturbation to the electronic structure. The newly-constructed emitters have demonstrated the precisely slight regulation of emission maxima of MR-TADF emitters to meet the actual industrial demand, and further enormously enriched the MR-TADF molecular reservoir. The BN-TP-N3-based OLED exhibits ultrapure green emission, with peak of 524 nm, full-width at half-maximum (FWHM) of 33 nm, Commission Internationale de L'Eclairage (CIE) coordinates of (0.23, 0.71), and maximum external quantum efficiency (EQE) of 37.3%.

Broadband near-infrared luminescence properties of Sc2(MoO4)3:Cr3+ molybdates

The structural and spectroscopic properties of Sc2(MoO4)3 molybdate containing various concentrations of Cr3+ ions were investigated in a temperature range of 80–300 K. The samples were prepared using hydrothermal as well as solid-state reaction methods. The influence of synthesis conditions and the molybdenum source on the structural properties was studied by X-ray diffraction (XRD), IR (infrared), and Raman methods. The optical properties of Sc2(MoO4)3 samples doped with 0.1, 0.5, 1.0, and 2.0 % of Cr3+ ions were investigated. The broadband near-infrared (NIR) luminescence spectra generated from the 4T2 and 2E levels of Cr3+ ions may be attractive for NIR light-emitting diode (LED) applications. Emission decay profiles and the crystal field parameters of Cr3+ ions are discussed. In particular, the mechanism of photoluminescence generation and the thermal quenching path are described in detail.

Spectral light quality regulates the morphogenesis, architecture, and flowering in pepper (Capsicum annuum L.).

Transparent plastic films with poor light transmittance seriously affect the mass composition of visible light in many greenhouses, which leads to the reduction of photosynthesis in vegetable crops. Understanding the regulatory mechanisms of monochromatic light in the vegetative and reproductive growth of vegetable crops is of great importance for the application of light-emitting diodes (LEDs) in the greenhouse. In this study, three monochromatic light treatments (red-, green- and blue-light) were simulated by using LEDs to explore light quality-dependent regulation from the stage of seedling to flowering in pepper (Capsicum annuum L.). The results showed that light quality-dependent regulation guides the growth and morphogenesis in pepper plants. Red- and blue-light played opposite roles in determining the plant height, stomatal density, axillary bud growth, photosynthetic characteristics, flowering time and hormone metabolism, while green light treatment resulted in taller plants and fewer branches, which was similar to the red-light treatment. The weighted correlation network analysis (WGCNA) based on mRNA-seq results revealed that the two modules named "MEred" and "MEmidnightblue" were positively correlated with red- and blue-light treatment, respectively, exhibiting high correlations with the traits such as plant hormone content, branching and flowering. Moreover, our results suggest that the light response factor ELONGATED HYPOCOTYL 5 (HY5) is essential for blue light-induced plant growth and development by regulating photosynthesis in pepper plants. Hence, this study uncovers crucial molecular mechanisms of how light quality determines the morphogenesis, architecture, and flowering in pepper plants, thus providing a basic concept of manipulating light quality to regulate pepper plant growth and flowering under greenhouse conditions.