Tunable Full Color Research Articles

A Modular Design of Continuously Tunable Full Color Plasmonic Pixels with Broken Rotational Symmetry

AbstractColor tuning is a fascinating and indispensable property in various applications. Thus far, a variety of reconfigurable approaches have been implemented to achieve color change. However, it is still a challenge to enable continuous color tuning over the entire hue range in a simple, stable, and rapid manner without changes in configuration and material properties. Here, an all‐optical continuously tunable plasmonic pixel scheme is demonstrated via a modular design approach to realize polarization‐controlled full color tuning by breaking the intrinsic symmetry of the unit cell layout. The polarization‐controlled full color tunable plasmonic pixels consist of three different types of color modules corresponding to three subtractive primary colors. Without changing the structural properties or surrounding environment, the structural colors can be continuously and precisely tuned across all hues by illuminating linearly polarized light with different polarization directions. Meanwhile, the plasmonic pixels can be flexibly customized for various color tuning processes through the appropriate choice of component modules and the elaborate design of module layouts. Furthermore, the color tuning is extended to achromatic colors with the utilization of a single module or the introduction of a black module. The proposed plasmonic pixels hold considerable potential to function as next‐generation color pixels integrated with liquid‐crystal polarizers.

Conditional controlled nano coordination polymers with tunable full color light emitting

Nanosized coordination polymers (NCPs) and their thin films with tunable full-color fluorescence emission, simple preparation, and good biocompatibility are highly desirable for optical and biomedical applications. Changes in the reaction conditions for fluorescent NCP@PEI and its thin films with tunable full-color emission are the first to be presented as the result of surface modification of PEI-induced band gap changes. Significantly, a white emitting fluorescence-calculated CIE value of (0.308, 0.312) can be observed by mixing NCP@PEI, and NCP@PEI-based poly (vinyl alcohol) (PVA) films with tunable full-color emission were obtained. The reaction condition effect is of particular importance for optical applications, where it can provide a new route to design NCP- or metal organic framework-based materials.

Color-Tunable, Excitation-Dependent, and Time-Dependent Afterglows from Pure Organic Amorphous Polymers.

Achieving persistent room-temperature phosphorescence (p-RTP), particularly those of tunable full-colors, from pure organic amorphous polymers is attractive but challenging. Particularly, those with tunable multicolor p-RTP in response to excitation wavelength and time are highly important but both fundamentally and technically underexplored. Here, a facile and general strategy toward color-tunable p-RTP from blue to orange-red based on amidation grafting of luminophores onto sodium alginate (SA) chains, resulting in amorphous polymers with distinct p-RTP and even impressively excitation-dependent and time-dependent afterglows is reported. p-RTP is associated with the unique semi-rigidified SA chains, effective hydrogen bonding network, and oxygen barrier properties of SA, whereas excitation-dependent and time-dependent afterglows should stem from the formation of diversified p-RTP emissive species with comparable but different lifetimes. These results outline a rational strategy toward amorphous smart luminophores with colorful, excitation-dependent, and time-dependent p-RTP, excellent solution processability, and film-forming ability for versatile applications.

Air-Stable Spirofluorene-Containing Ladder-Type Bis(alkynyl)borane Compounds with Readily Tunable Full Color Emission Properties.

A series of air-stable spiro-fused ladder-type boron(III) compounds has been designed, synthesized, and the electrochemistry and photophysical behavior have been characterized. By simply varying the substituents on the pyridine ring and extending the π-conjugation of the spiro framework, the emission color of these compounds can be easily fine-tuned spanning the visible spectrum from blue to red. All compounds exhibit a broad and structureless emission band across the entire visible region, assigned as an intramolecular charge-transfer transition originating from the thiophene of the spiro framework to the pyridine-borane moieties. In addition, these compounds demonstrate high photoluminescence quantum yields of up to 0.81 in dichloromethane solution and 0.86 in doped thin films. Some of the compounds have also been employed as emissive materials, in which solution-processed organic light-emitting devices (OLEDs) with tunable emission colors spanning the visible spectrum from blue, green to red have been realized, demonstrating the potential applications of these boron compounds in OLEDs.

A single-phase Ba9Lu2Si6O24:Eu2+, Ce3+, Mn2+ phosphor with tunable full-color emission for NUV-based white LED applications

We obtained a single phase BLS:Eu2+, Ce3+, Mn2+ phosphor by solid-state reactions. Eu2+, Ce3+, and Mn2+ gives rise to the blue, green, and red emission, respectively. The Mn2+ red emission can be effectively enhanced via energy transfers from both Eu2+ and Ce3+. Thus a tunable full color emission from 410 to 750nm was realized in this single phosphor. The Eu2+→Mn2+ energy transfer mechanism was investigated by the fluorescence decay curves. This single phosphor exhibits an efficient excitation band covering from 390 to 410nm, which matches well with the emission light of the efficient NUV chips. The optimized BLS:Eu2+, Ce3+, Mn2+ phosphor shows a high quantum efficient of ∼62% and a good color stability. When this single phosphor was combined with a 395nm NUV-chip, an ideal white LED with a high color render index (CRI) of 85 and a correlated color temperature (CCT) of 6300K was obtained. This demonstrates the promising application of the BLS:Eu2+, Ce3+, Mn2+ single phosphor for the NUV-based white LEDs.

The spectroscopic properties of Dy3+and Eu3+ co-doped Y3Al5O12 (YAG) phosphors for white LED

Tunable full color emissive Y2.94−xAl5O12: 0.06Dy3+, xEu3+ (YAG: 0.06Dy, xEu) phosphors with emission peaks at 483nm (blue), 582nm (yellow) and 610nm (red) were synthesized by a sol–gel method. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), photoluminescence decay lifetimes, photoluminescence excitation and emission spectra. The results showed that photoluminescence intensity varied with excitation wavelength and the doping concentration of Eu3+. The co-doping with Eu3+ compensated the red emission component of the YAG: Dy3+ phosphor. The chromaticity coordinate of YAG: 0.06Dy, 0.09Eu phosphor (0.3263, 0.3334) was very close to that of the ideal white light (0.3333, 0.3333). Thus, the YAG: 0.06Dy, 0.09Eu phosphor can find potential application in simulating the sunlight artificially through fabricating white light emitters.

Color-tunable, phosphor-free InGaN nanowire light-emitting diode arrays monolithically integrated on silicon.

We demonstrate controllable and tunable full color light generation through the monolithic integration of blue, green/yellow, and orange/red InGaN nanowire light-emitting diodes (LEDs). Such multi-color nanowire LED arrays are fabricated directly on Si substrate using a three-step selective area molecular beam epitaxy growth process. The lateral-arranged multi-color subpixels enable controlled light mixing at the chip-level and yield color-tunable light emission with CCT values in the range from 1900 K to 6800 K, while maintaining excellent color rendering capability. This work provides a viable approach for achieving micron and nanoscale tunable full-color LED arrays without the compromise between the device efficiency and light quality associated with conventional phosphor-based LEDs.

White light emission and energy transfer in Dy3+/Eu3+ co-doped BaLa2WO7 phosphors

Tunable full color emissive BaLa1.75−xWO7:0.25Dy3+, xEu3+ phosphors which peaked at 484nm (blue), 572nm (yellow), 593nm (orange), and 617nm (red) were synthesized by the traditional solid-state reaction method. The as-synthesized phosphors were characterized by X-ray power diffraction, diffused reflectance spectra, photoluminescence decay curves, photoluminescence excitation and emission spectra. The photoluminescence excitation spectra range from 200 to 500nm, including an O2−⟶W6+ charge transfer band and several 4f–4f transition peaks of Dy3+ and Eu3+. Co-doping with Eu3+ compensated the red emission component of the BaLa2WO7:Dy3+ phosphor. Furthermore, the energy transfer from Dy3+ to Eu3+ was confirmed based on the luminescence spectra and decay curves. The intense white light emissions are suggestive exploration for the potential phosphor for optical materials applications used in the ultraviolet excited white light emitting diodes.

Tunable full color emission from single-phase LiSr3.99−xDy0.01(BO3)3:xEu3+ phosphors

Abstract Tunable full color emissive LiSr3.99−xDy0.01(BO3)3:xEu3+ (0≤x≤0.09) phosphors peaked at 481 nm (blue), 574 nm (yellow), 592 nm (orange), and 617 nm (red) were synthesized in air by high temperature solid-state reaction route. The as-synthesized phosphors were characterized by X-ray powder diffraction (XRD), photoluminescence excitation (PLE) and photoluminescence (PL) spectra. The PLE spectra in the range from 200 to 500 nm include an Eu–O charge transfer band (CTB) and several 4f–4f transition peaks of Dy3+ and Eu3+, indicating its potential application in white light emitting diodes (LEDs). The effect of Eu3+ concentration on the emission intensity of LiSr3.99−xDy0.01(BO3)3:xEu3+ phosphors was investigated in detail and the optical concentration is found to be x=0.005. The CIE chromaticity coordinates for LiSr3.99−xDy0.01(BO3)3:xEu3+ phosphors are simulated. With an increase in Eu3+ ion concentration, the chromaticity color coordinates can be tuned efficiently from the border of greenish white region to its equal-energy white light point, and eventually to red region. All the results imply that the studied LiSr3.99−xDy0.01(BO3)3:xEu3+ phosphors could be potentially used as white LEDs.

Electrically tunable block copolymer photonic crystals with a full color display

Electrically tunable full color display photonic crystals (PCs) made of a thin film of block copolymer, polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP), have been developed. The phase separation of PS and P2VP blocks leads to a one-dimensional periodic lamellar structure parallel to the surface of the thin film. In a solvent mixture of water and ethanol, each P2VP layer is swollen and partially charged. Applying a low voltage (<2.5 V) to such a thin film can lead to the repeatable expansion or contraction of each P2VP layer, depending on the direction and strength of the electrical potential. Such a variation of the lamellar periodicity leads to a full color display over a wide range from ultraviolet to near infrared. The advantages of such PCs are their facile preparation, low driving voltage and good durability, which make them potentially useful in information technologies.