Manipulating Luminescence of Light Emitters by Photonic Crystals

Part & Part Syst Charact

et al. 2020

printing, [23][24][25][26][27][28][29] anticounterfeiting, [30][31][32][33][34][35][36][37][38] photo catalysis, [39][40][41] optical device, [42][43][44][45][46] and solar energy. [47][48][49][50] According to the order degree of the structures, the PCs can be divided into highly ordered photonic crystals (OPCs) and amorphous photonic crystals (APCs). These two kinds of PCs show considerable difference in the optical properties. The OPCs with long-range ordered structures show iridescent structural colors, while the APCs with only short-range order exhibit non-iridescent structural colors. For some applications, such as color displays or sensors, [51][52][53][54] angle independent colors are necessary and required. In this regard, APCs with angle independent structural colors show inherent advantages than the OPCs owing to the amorphous packing of the particles. However, the fabrication of APCs remains a big challenge. In particular, the charged colloidal particles tend to crystalize and form long-range order upon the assembly process, which make it rather difficult to prepare APCs.Recently, there have been attempts to fabricate APCs through the dynamic or thermodynamic controlling the assembly process. Spray [55,56] and infiltration [57] are efficient in preparing APCs based on the rapid remove of solvents from the colloidal solution, respectively. In both approaches, the fast remove of solvents will break the longrange packing tendency of particles, resulting in the shortrange order. However, the usage of the environmentally harmful solvent or porous substrates in these two methods will limit their practical utility. Layer by layer strategy [58] is promising in preparing APCs based on consecutively polyelectrolyte coating process but subjected to the tedious and time-consuming processes. Although the bi-disperse suspension [59,60] is successful for fabrication of APCs, it is essential to control the difference in particle size to guarantee the bright colors of APCs. Alternatively, APCs can be fabricated by the self-assembly of soft particles. [61,62] With this approach, subtle fabrications must be well controlled to ensure the success of controlling the thickness of the shell and the assembly of soft particles. Except for the fabrication, the APCs usually exhibit pale structural colors due to the strong multiple scattering light. To deal with this problem, carbon black or other black particles are introduced into the APCs to absorb the Facile and efficient fabrication of amorphous photonic crystals (APCs) with uniform and angle independent structural colors is highly desired due to their unique applications in non-iridescent colors-based displays, pigments, and sensors. Here, a solvent-assisted colloidal assembly approach is reported to fabricate APCs with uniform and angle-independent structural colors by the self-assembly of polydopamine-embedded silica particles in pentanol. The surface charge of the particle mediated by the polarity of solvent is demonstrated to be the key to control the particle arrangeme...

Section: Introductionmentioning

confidence: 99%

Highly Efficient Fabricating Amorphous Photonic Crystals Using Less Polar Solvents and the Wettability‐Based Information Storage and Recognition

Yang

Part & Part Syst Charact

et al. 2020

“…Rare earth (RE) ion‐doped materials have been developed as significant gain matrices due to their high photoluminescence quantum yield (PLQY) and multiple‐wavelength luminescence . Recent decades have witnessed extensive investigations in doping methods and network structure design to obtain more efficient gain materials . However, the requirements for high luminescence efficiency and excellent thermodynamic stability of optical materials are always contradictory, greatly restricting their applications in, e.g., high‐temperature, high‐humidity, and high‐power laser pumping environments.…”

mentioning

confidence: 99%

Phase‐Separation Engineering of Glass for Drastic Enhancement of Upconversion Luminescence

Fang

Advanced Optical Materials

Peng

et al. 2019

earth (RE) ion-doped materials have been developed as significant gain matrices due to their high photoluminescence quantum yield (PLQY) and multiple-wavelength luminescence. [4,5] Recent decades have witnessed extensive investigations in doping methods and network structure design to obtain more efficient gain materials. [6,7] However, the requirements for high luminescence efficiency and excellent thermodynamic stability of optical materials are always contradictory, greatly restricting their applications in, e.g., high-temperature, high-humidity, and high-power laser pumping environments. Generally, the luminescence efficiency of an optical material is inversely proportional to the multiphonon nonradiative transition probability (W p ) of the intermediate state energy level for RE ions. [8] The luminescence process, especially for the upconversion (UC) process, is normally associated with a large number of intermediate state energy levels. Furthermore, its value (W p ) depends on the maximum phonon energy (ћω) of the elastic structure of condensed matter, and it increases dramatically with increasing ћω (as described in Equations (S1)-(S3) of the Supporting Information). [9] Traditionally, one class of soft material with extremely low ћω values, including fluorides, chalcogenides, and halogenides, has been widely Optical gain materials are of fundamental importance for various applications, such as lasers, lighting, optical communication, microscopy, and spectroscopy. However, the requirements for high luminescence efficiency and excellent thermodynamic stability of materials are always contradictory. As a result, wide applications of optical materials in high-temperature, high-humidity, and high-power laser-irradiated environments are restricted. Here, a facile approach based on phase-separation engineering is proposed to modulate the thermodynamic stability and enhance the luminescence efficiency of optical gain materials. It is shown that the thermodynamic stability and luminescence efficiency of the phase-separated fluorosilicate (FS) gain glass are both enhanced dramatically when the SiO 2 concentration is optimized. Owing to the confinement effect of phase-separation network structure on active ions, the upconversion (UC) luminescence efficiency of the designed glass is 150 times higher than that of traditional FS glasses and even seven times higher than that of ZBLAN (ZrF 4 -BaF 2 -LaF 3 -AlF 3 -NaF) glass, which is the most commonly used material for UC fiber lasing applications. These intriguing properties of the glass indicate that phase-separation engineering not only provides a powerful solution to conquer the conventional contradiction between thermodynamic stability and luminescence efficiency but also offers significant opportunities for manufacturing a wide range of optical composites with multiple functions.

“…Manipulation of luminescence by photonic crystals has been well summarized in a former review. [ 136 ] Effective Bragg reflections could significantly enhance the light extraction (external quantum efficiency); [ 137–140 ] the slow photon effect could boost light absorption as the light slows down at the edges of the stop bands, increasing the light absorption. [ 141,142 ] On the contrary, when the stop band overlaps with the emission band, effective inhibitions occur as the emission light of corresponding wavelengths cannot propagate inside the photonic crystals, [ 143–146 ] providing highly tunable emission spectra and the resultant diversified anticounterfeiting designs.…”

Section: Strategies For Anticounterfeiting Via Structural Colorsmentioning

confidence: 99%

Structural Color Materials for Optical Anticounterfeiting

Hong

Yuan

2020

Small

306

251

The counterfeiting of goods is growing worldwide, affecting practically any marketable item ranging from consumer goods to human health. Anticounterfeiting is essential for authentication, currency, and security. Anticounterfeiting tags based on structural color materials have enjoyed worldwide and long‐term commercial success due to their inexpensive production and exceptional ease of percept. However, conventional anticounterfeiting tags of holographic gratings can be readily copied or imitated. Much progress has been made recently to overcome this limitation by employing sufficient complexity and stimuli‐responsive ability into the structural color materials. Moreover, traditional processing methods of structural color tags are mainly based on photolithography and nanoimprinting, while new processing methods such as the inkless printing and additive manufacturing have been developed, enabling massive scale up fabrication of novel structural color security engineering. This review presents recent breakthroughs in structural color materials, and their applications in optical encryption and anticounterfeiting are discussed in detail. Special attention is given to the unique structures for optical anticounterfeiting techniques and their optical aspects for encryption. Finally, emerging research directions and current challenges in optical encryption technologies using structural color materials is presented.