Recent Advances in Patterning Strategies for Full‑Color Perovskite Light‑Emitting Diodes

Metal halide perovskites have emerged as promising light-emitting materials for next-generation displays owing to their remarkable material characteristics including broad color tunability,pure color emission with remarkably narrow bandwidths,high quantum yield,and solution processability.Despite recent advances have pushed the luminance efficiency of monochromic perovskite light-emitting diodes(PeLEDs)to their theoretical limits,their current fabrication using the spincoating process poses limitations for fabrication of full-color displays.To integrate PeLEDs into full-color display panels,it is crucial to pattern red–green–blue(RGB)perovskite pixels,while mitigating issues such as cross-contamination and reductions in luminous efficiency.Herein,we present state-of-the-art patterning technologies for the development of full-color PeLEDs.First,we highlight recent advances in the development of efficient PeLEDs.Second,we discuss various patterning techniques of MPHs(i.e.,photolithography,inkjet printing,electron beam lithography and laserassisted lithography,electrohydrodynamic jet printing,thermal evaporation,and transfer printing)for fabrication of RGB pixelated displays.These patterning techniques can be classified into two distinct approaches:in situ crystallization patterning using perovskite precursors and patterning of colloidal perovskite nanocrystals.This review highlights advancements and limitations in patterning techniques for PeLEDs,paving the way for integrating PeLEDs into full-color panels.

Rh(Ⅲ)-Catalyzed sequential ring-retentive/-opening [4+2]annulations of 2H-imidazoles towards full-color emissive imidazo[5,1-a]isoquinolinium salts and AIE-active non-symmetric 1,1-biisoquinolines

Rhodium-catalyzed C4aryl-H activation and ring-retentive annulation of 2H-imidazoles with internal alkynes to build imidazo[5,1-a]isoquinolinium salts with high yields and broad scope has been disclosed.These novel salts serve as new full-color emissive fluorophores(433-633 nm),just by simply modifying the substituents on C3 and C4 positions of isoquinoline ring.Furthermore,these salts can undergo ring-opening C5_(aryl)-H activation/annulation with a different alkyne to form non-symmetric and AIE-active1,1-biisoquinolines,where NH_(4)OAc plays an indispensable role that accounts for Hofmann elimination and imine formation,leading to an unprecedented imine dance:cyclic imine→N-alkenyl imine→NH imine.The15N labelling experiments indicate that the 2ndannulation includes two pathways:N-exchange(major)and N-retention(minor).

One-dimensional molecular co-crystal alloys capable of full-color emission for low-loss optical waveguide and optical logic gate

The luminescence color of molecule-based photoactive materials is the key to the applications in lighting and optical communication.Realizing continuous regulation of emission color in molecular systems is highly desirable but still remains a challenge due to the individual emission band of purely organic molecules.Herein,a novel alloy strategy based on molecular co-crystals is reported.By adjusting the molar ratio of pyrene(Py)and fluorathene(Flu),three types of molecular co-crystal alloys(MCAs)assemblies are prepared involving Py-Flu-OFN-x%,Py-Flu-TFP-x%,Py-Flu-TCNB-x%.Multiple energy level structure and Förster resonance energy transfer(FRET)process endow materials with tunable full-spectra emission color in visible region.Impressively,these MCAs and co-crystals can be successfully applied to low optical loss waveguide and optical logic gate by virtue of all-color luminescence from blue across green to red,together with smooth surface of onedimensional microrods,which show promising applications as continuous light emitters for advance photonics applications.

Characteristics and techniques of GaN-based micro-LEDs for application in next-generation display

Due to the excellent optoelectronic properties,fast response time,outstanding power efficiency and high stability,micro-LED plays an increasingly important role in the new generation of display technology compared with LCD and OLED display.This paper mainly introduces the preparation methods of the GaN-based micro-LED array,the optoelectronic characteristics,and several key technologies to achieve full-color display,such as transfer printing,color conversion by quantum dot and local strain engineering.

Bi_(2)O_(2)Se nanoplates for broadband photodetector and full-color imaging applications

Broadband light detection and sensing are widely applied in modern technology.As a promising candidate for next-generation two-dimensional(2D)optoelectronic material,bismuth oxyselenide(Bi_(2)O_(2)Se)nanoplates exhibit many prospects in the application of visible light detection due to their peculiar properties.In this work,we report the photodetection performance of single-crystal 2D Bi_(2)O_(2)Se nanoplates grown on SiO_(2)based on a ternary-alloy growth model by utilizing chemical vapor deposition(CVD).The Bi_(2)O_(2)Se nanoplates were found to have an even and uniform square shape with side lengths up to 15μm and an approximate thickness of 15 nm.A visible-light photodetector was fabricated based on a CVD-grown Bi_(2)O_(2)Se nanoplate,and characterized by a set of illumination experiments using a 400 nm laser at temperatures ranging from 77 to 370 K.The device exhibited superior performance at the temperature of 77 K,with a responsivity of 523 A/W,a specific detectivity of 1.37×10^(11)Jones,a response time of 0.2175 ms,an external quantum efficiency of 162,119.44%,resulting in high-quality and fullcolor imaging in the visible spectrum.These results indicate that the single-crystalline Bi_(2)O_(2)Se nanoplates have excellent potential in broadband photodetection and non-cryogenic imaging.

Memorable full-color circularly polarized luminescence from chiral co-assembled polymer films enabled by multipath transfer

The modulation of circularly polarized luminescence(CPL)is of importance for display and asymmetric chemical synthesis.However,the underlying mechanism of CPL transfer remains rarely studied.Herein,we rationally design a multipath transfer system including multistep chirality transfer(MCT)and sequential fluorescence resonance energy transfer(SFRET),and we are the first to fabricate memorable full-color CPL-active films with a high dissymmetry factor(~10^(-2)).Specifically,(P/M)-helical nanofibers are constructed by co-assembly between an achiral polymer,poly(9,9-di-n-octylfluorene)(PF8),and easy-to-remove R/S-limonene.When matching achiral emitters are added,the PF8 mediates MCT and simultaneously triggers the SFRET process.Furthermore,full-color CPL memory is realized after removing the chiral source.Molecular simulation and structure analysis indicate that the robust helical superstructure of PF8 provides chiral sites to accommodate emitters,which is essential for CPL transfer and memory.This work provides a novel strategy for constructing CPL-active materials in an aggregated state and insights into CPL transfer and memory.

Preparation of multicolor carbon dots with thermally turn-on fluorescence for multidimensional information encryption

Carbon dots(CDs)with superior fluorescence properties have attracted a growing number of research interests in anti-counterfeiting.However,the preparation of CDs with thermally turn-on fluorescence and full-color-emitting in visible spectrum is still a big challenge due to the complicated reaction mechanism in the formation of CDs.Here,a simple precursor-oriented strategy for the preparation of multicolor CDs with heat-stimuli turn-on fluorescence is reported.Comprehensive experimental characterizations and theoretical calculations revealed that the emission wavelength of CDs can be readily tuned from 460 nm to 654 nm with selected precursors,which was ascribed to the extent of conjugated sp2-domains(core states)and the amount of oxygen-and nitrogen-containing groups bound to sp2-domains(surface states).After simply mixing two or three kinds of CDs,a full-color range of fluorescence emission was realized,and the CDs-based fluorescence inks were successfully fabricated.Particularly,all the printed patterns from the inkjet exhibited a thermal-induced enhancement in fluorescence.On this basis,combining CDs with heating-induced“turn-off”fluorescence materials can lead to multidimensional and multistage encryption.These results demonstrate that the thermochromic and photochromic CDs with much more enhanced security exhibit promising application in data storage and encryption.

Full-color monolithic hybrid quantum dot nanoring micro light-emitting diodes with improved efficiency using atomic layer deposition and nonradiative resonant energy transfer

Full-color displays based on micro light-emitting diodes(μLEDs) can be fabricated on monolithic epitaxial wafers. Nanoring(NR) structures were fabricated on a green LED epitaxial wafer; the color of NR-μLEDs was tuned from green to blue through strain relaxation. An Al_2O_3 layer was deposited on the sidewall of NR-μLEDs,which improved the photoluminescence intensity by 143.7%. Coupling with the exposed multiple quantum wells through nonradiative resonant energy transfer, red quantum dots were printed to NR-μLEDs for a full-color display. To further improve the color purity of the red light, a distributed Bragg reflector is developed to reuse the excitation light.

Large scale synthesis of full-color emissive carbon dots from a single carbon source by a solvent-free method

Full-color emissive carbon dots(CDs)hold a great promise for various applications,especially in light emitting diodes(LEDs).However,the existing synthetic routes for CDs are carried out in solutions,which suffer from low yields,high pressures,various byproducts,large amounts of waste solvents,and complicated photoluminescence(PL)origins.Therefore,it is necessary to explore large scale synthesis of CDs with high quantum yield(QY)across the entire visible range from a single carbon source by a solvent-free method.In this work,a series of CDs with tunable PL emission from 442 to 621 nm,QY of 23%-56%,and production yield within 34%-72%,are obtained by heating o-phenylenediamine with the catalysis of KCl.Detailed characterizations identify that,the differences between these CDs with respect to the graphitization degree,graphitic nitrogen content,and oxygen-containing functional groups,are responsible for their distinct optical properties,which can be modulated by controlling the deamination and dehydrogenation processes during reactions.Blue,green,yellow,red emissive films,and LEDs are prepared by dispersing the corresponding CDs into polyvinyl alcohol(PVA).All types of white LEDs(WLEDs)with high colorrendering-index(CRI),including warm WLEDs,standard WLEDs,and cool WLEDs,are also fabricated by mixing the red,green,and blue emissive CDs into PVA matrix by the appropriate ratios.

Optical cross-talk reduction in a quantumdot-based full-color micro-light-emitting-diode display by a lithographic-fabricated photoresist mold

In this study, a full-color emission red–green–blue(RGB) quantum-dot(QD)-based micro-light-emitting-diode(micro-LED) array with the reduced optical cross-talk effect by a photoresist mold has been demonstrated. The UV micro-LED array is used as an efficient excitation source for the QDs. The aerosol jet technique provides a narrow linewidth on the micrometer scale for a precise jet of QDs on the micro-LEDs. To reduce the optical cross-talk effect,a simple lithography method and photoresist are used to fabricate the mold, which consists of a window for QD jetting and a blocking wall for cross-talk reduction. The cross-talk effect of the well-confined QDs in the window is confirmed by a fluorescence microscope, which shows clear separation between QD pixels. A distributed Bragg reflector is covered on the micro-LED array and the QDs' jetted mold to further increase the reuse of UV light.The enhanced light emission of the QDs is 5%, 32%, and 23% for blue, green, and red QDs, respectively.

Advances, opportunities, and challenge for full-color emissive carbon dots

Carbon dots(CDs), novel luminescent zero-dimensional carbon nanomaterials, have been widely applied due to their low toxicity, optimal optical properties, and easy modification. However, the current controllable equipment and mechanism explanation of CDs are relatively vague and require urgent resolution.Full-color emission CDs, an essential CDs category, have attracted people’s attention given their light and color-tunable properties. In addition to a wider range of biological and optoelectronic device applications, full-color emission CDs have similar structures and significantly affected the fluorescence mechanism of CDs. At present, few studies have reported on the summary research of CDs emitted by its full color, which greatly limits the development of CDs mechanisms and applications. As such, the present review detailed the full-color CDs development status, to which a suitable method for preparing full-color CDs was presented and the existing fluorescence emission mechanism of full-color CDs was summarized.Herein, we comprehensively introduced full-color CDs applications in biology and optoelectronics. Finally,we made an outlook on the development and potential applications of full-color CDs. The present review aims to contribute novel insights and methods for understanding full-color CDs.

Sub-ambient full-color passive radiative cooling under sunlight based on effcient quantum-dot photoluminescence

Daytime radiative cooling with high solar refection and mid-infrared emission offers a sustainable way for cooling without energy consumption.However,so far sub-ambient daytime radiative coolers typically possess white/silver color with limited aesthetics and applications.Although various colored radiative cooling designs have been pursued previously,multi-colored daytime radiative cooling to a temperature below ambient has not been realized as the solar thermal effect in the visible range lead to signifcant thermal load.Here,we demonstrate that photoluminescence(PL)based colored radiative coolers(PCRCs)with high internal quantum effciency enable sub-ambient full-color cooling.As an example of experimental demonstration,we develop a scalable electrostatic-spinning/inkjet printing approach to realize the sub-ambient multi-colored radiative coolers based on quantum-dot photoluminescence.The unique features of obtained PCRCs are that the quantum dots atop convert the ultraviolet–visible sunlight into emitted light to minimize the solar-heat generation,and cellulose acetate based nanofbers as the underlayer that strongly refect sunlight and radiate thermal load.As a result,the green,yellow and red colors of PCRCs achieve temperatures of 5.4–2.2℃ below ambient under sunlight(peak solar irradiance>740 Wm),respectively.With the excellent cooling performance and scalable process,our designed PCRC opens a promising pathway towards colorful applications and scenarios of radiative cooling.

Full-color quantum dots active matrix display fabricated by ink-jet printing

Making full-color active matrix display based on quantum dot light emitting diodes(AM-QLEDs) via ink-jet printing is attractive in display industry due to QLEDs' wide color gamut and their potential manufacturing advantages of large screen size and low cost. The challenges for realizing AM-QLED display are how to achieve high quality films through ink-jet printing, multi-color patterning, electroluminescence(EL) color purity, and high efficiency. Herein, a 2-inch diagonal full-color AM-QLEDs display with pixel density of 120 pixels per inch(PPI) fabricated by ink-jet printing technique is presented. Driven by a metal oxide TFT(MOTFT) back-panel, the display exhibits a maximum brightness of 400 cd m.2, and a color gamut of 109%(NTSC 1931). The red, green, and blue(RGB) monochrome QLEDs passive matrix panels fabricated by ink-jet printing technique have a current efficiency(CE) of 2.5, 13.9, and 0.30 cd A.1, respectively. To the best of our knowledge, the efficiencies are the highest among passive matrix QLEDs panels made by ink-jet printing technique. The ink-jet printed QDs films show good thickness uniformity due to high viscosity and low volatility of the printable inks, and no cross-contamination between adjacent pixels resulting from the hydrophobic pixel defining layer.

Holographic imaging of full-color real-existing three-dimensional objects with computer-generated sequential kinoforms

We propose a computational method for generating sequential kinoforms of real-existing full-color three- dimensional （3D） objects and realizing high-quality 3D imaging. The depth map and color information are obtained using non-contact full-color 3D measurement system based on binocular vision. The obtained full-color 3D data are decomposed into multiple slices with RGB channels. Sequential kinoforms of each channel are calculated and reconstructed using a Fresnel-diffraction-based algorithm called the dynamic- pseudorandom-phase tomographic computer holography （DPP-TCH）. Color dispersion introduced by different wavelengths is well compensated by zero-padding operation in the red and green channels of object slices. Numerical reconstruction results show that the speckle noise and color-dispersion are well suppressed and that high-quality full-color holographic 3D imaging is feasible. The method is useful for improving the 3D image quality in holographic displays with pixelated phase-type spatial light modulators （SLMs）.

One-pot synthesis of concentration and excitation dual-dependency truly full-color photoluminescence carbon dots

The paper describes a kind of truly full-color photoluminescence(PL)CDs.The CDs were prepared by using one-pot hydrothermally heating citric acid and formamide at 200℃ for 2 h.The CDs have three fluorescent centers at blue,green,and red light region.Their color was regulated through two means,including changing excitation wavelengths or CDs concentrations.The emission maxima changed from blue to red with the increase of excitation wavelengths or CDs concentrations.The full-color PL behavior of the CDs was inherited and conserved in the solid polymer matrix,giving multicolor CDs/polymer films and light emitting diodes(LEDs).White-light LED(WLED)with the CIE coordinate approaching to(0.31,0.32)were also achieved.

Quantum-dot and organic hybrid light-emitting diodes employing a blue common layer for simple fabrication of full-color displays

Colloidal quantum-dot(QD)light-emitting diodes(QLEDs)have been in the forefront of future display devices due to their outstanding optoelectronic properties.However,a complicated solution-process for patterning the red,green,and blue QDs deteriorates the QLED performance and limits the resolution of full-color displays.Herein,we report a novel concept of QD–organic hybrid light-emitting diodes by introducing an organic blue common layer(BCL)which is deposited through a common mask over the entire sub-pixels.Benefitted from the optimized device structure,red and green QLEDs retained their color coordinates despite the presence of the BCL.Furthermore,adopting the BCL improved the external quantum efficiency of green and red QLEDs by 38.4%and 11.7%,respectively,due to the Förster resonance energy transfer from the BCL to the adjacent QD layers.With the BCL structure,we could simply demonstrate a full-color QD-organic hybrid device in a single substrate.We believe that this device architecture is practically applicable for easier fabrication of solution-processed,highresolution,and full-color displays with reduced process steps.

Full‑Color Tunable and Highly Fire‑Retardant Colored Carbon Fibers

Carbon fibers(CFs)are widely used in various cutting-edge fields,such as aerospace,military,automobiles,and sports,owing to their unique combination of excellent mechanical properties,good thermal stability,and lightweight.However,their inherent super-black appearance makes it difficult to satisfy the aesthetic/fashion requirements of the colorful world,and the flammability of CFs severely limits their practical utilization in high-temperature and other extreme environments.Herein,we fabricated full-color tunable colored CFs on a large-scale via atomic layer deposition,based on the monolayer film interference strategy.CFs exhibited brilliant colors and excellent environmental durability in extreme environments,such as intense ultraviolet(UV)irradiation,accelerated laundering,friction,high-temperature,and low-temperature treatments.Colored CFs also exhibited excellent fire-retardant performance that could withstand alcohol-lamp flame burning for 60 min.Our work provides insights into an innovative material/structural design that can help achieve rapid development of the CF industry and global carbon neutrality/sustainability.

调控分子间的电子耦合效应实现多彩超长有机室温磷光

有机超长室温磷光聚合物因其优异的可加工性、灵活性和可重复性等特点,在各种光电应用中表现出巨大的应用潜力.然而,实现全彩的室温磷光仍然是一个挑战.在本文中,我们通过在聚乙烯醇中掺杂不同浓度的三苯基膦盐,成功制备了一系列余晖颜色可调的有机室温磷光聚合物(从蓝色到红色).实验和理论计算证明:室温磷光聚合物颜色的宽范围调控归因于掺杂体膦盐分子间的电子耦合作用大小.此外,这些多彩的磷光聚合物可应用于柔性3D显示和防伪.

Dual upconversion nanophotoswitch for security encoding

Light-harvesting lanthanide ions(Ln3+) doped NaYF4 inks could provide polychromatic patterns for opposing counterfeiting commodity infestation because of their distinctive upconversion photoluminescence(UPL) properties. Herein, three kinds of core-triple-shell Ln3+ions doped NaYF4 upconversion nanocrystals(UCNCs) are synthesized through modified high-temperature coprecipitation, which demonstrate excellent UPL properties of independent emitting colors under 808 or 980 nm laser excitation. Additive mixing three kinds of 808 nm emitted red-green-blue(RGB)UCNCs colloid solution can precisely regulate the emissions of the suspension for achieving full-color display. The as-obtained RGB three-primary colors induced by 808 nm laser accomplish broader color gamut than traditional standard RGB(s RGB) model and printing cyan-magenta-yellow(CMY)model. In addition, various China zodiac patterns and complex multicolor images are printed by the as-formulated UCNCs inks through screen printing technology. The printed patterns present colorful and polychromatic sequential toning visualization patterns under 808 nm excitation, while present another succession of gradually changed versatile patterns under 980 nm excitation. As a proof of concept, transparent polyvinyl chloride(PVC) self-adhesive anti-counterfeiting label is attached to the bottle of wine package for practical application. The demonstration of multiple model patterns of Chinese zodiac and poetry images based on these core-tripleshell UCNCs can be selected as a conceivable substitute of traditional single model patterns, underlining the full-color anti-counterfeiting level.