Enhancement of Light Efficiency of Deep-Ultraviolet Light-Emitting Diodes by Encapsulation with a 3D Photonic Crystal Reflecting Layer.

Recently, UVC LEDs, which emit deep ultraviolet light, have found extensive applications across various fields. This study demonstrates the design and implementation of thin films of three-dimensional photonic crystals (3D PhCs) as reflectors to enhance the light output power (LOP) of UVC LEDs. The 3D PhC reflectors were prepared using the self-assembly of silica nanospheres on a UVC LED lead frame substrate via the evaporation-induced method (side) and the gravitational sedimentation method (bottom), respectively. These PhCs with the (111) crystallographic plane were deposited on the side wall and bottom of the UVC LED lead frame, acting as functional materials to reflect UVC light. The LOP of UVC LEDs with 3D PhC reflectors at a driving current of 100 mA reached 19.6 mW. This represented a 30% enhancement compared to commercial UVC LEDs with Au-plated reflectors, due to the UVC light reflection by the photonic band gaps of 3D PhCs in the (111) crystallographic plane. Furthermore, after aging tests at 60 °C and 60% relative humidity for 1000 h, the relative LOP of UVC LEDs with 3D PhC reflectors decreased by 7%, which is better than that of commercial UVC LEDs. Thus, this study offers potential methods for enhancing the light output efficiency of commercial UVC light-emitting devices.

CCT- and CRI-tuning of white light-emitting diodes using three-dimensional non-close-packed colloidal photonic crystals with photonic stop-bands.

This study exhibited the correlated color temperature (CCT)- and color-rendering index (CRI)-tuning behavior of light emission from white light-emitting diodes (WLEDs) using three-dimensional non-close-packed (3D NCP) colloidal photonic crystals (CPhCs). The CCT of approximately 5300 K (characteristic of cold WLEDs) of white light propagated through the NCP CPhCs dropped to 3000 K (characteristic of warm WLEDs) because of the photonic stop-bands based on the photonic band structures of NCP CPhCs. This study successfully developed a novel technique that introduces lower-cost CCT- and CRI-tuning cold WLEDs with a CRI of over 90 that of warm WLEDs by using 3D NCP CPhCs.

Light-spectrum modification of warm white-light-emitting diodes with 3D colloidal photonic crystals to approximate candlelight.

This study presents the light-spectrum modification of warm white-light-emitting diodes (w-WLEDs) with 3D colloidal photonic crystals (3D CPhCs) to approximate candlelight. The study measures the angular-resolved transmission properties of the w-WLEDs with CPhCs, which exhibit photonic stop bands based on the CPhC photonic band structures. The w-WLEDs with 3D CPhCs produce a low correlated color temperature of 1963 K, a high color-rendering index of 85, and a luminous flux of 22.8 lm (four times that of a candle). This study presents the successful development of a novel low-cost technique to produce candlelight w-WLEDs for use as an indoor light source.

Highly bright broadband red light produced by fluorescence polymer/InGaN hybrid light-emitting diodes.

The fabrication of fluorescence polymer/InGaN hybrid light-emitting diodes (LEDs) that emit highly bright broadband red light is presented in this Letter. The absorption peak of the fluorescence polymer was 455 nm, and the emission peak was 640 nm. The light output power and external quantum efficiency of hybrid LEDs at a driving current of 100 mA were 46.6 mW and 24.1%, respectively. The emission spectrum of hybrid LEDs was located at a wavelength of 641 nm, with a broadband FWHM of 106 nm. Thus this study offers potential methods for enhancing the output power of commercial white-light-emitting devices.

Enhanced and Extended Ophthalmic Drug Delivery by pH-Triggered Drug-Eluting Contact Lenses with Large-Pore Mesoporous Silica Nanoparticles.

Drug-eluting contact lenses (DCLs) have attracted considerable attention as potential therapeutic ophthalmic drug delivery devices. In this study, we propose, fabricate, and investigate pH-triggered DCLs that are combined with large-pore mesoporous silica nanoparticles (LPMSNs). Compared to reference DCLs, LPMSN-laden DCLs can prolong the residence time of glaucoma drugs in an artificial lacrimal fluid (ALF) environment at pH 7.4. Additionally, LPMSN-laden DCLs do not require drug preloading and are compatible with current contact lens manufacturing processes. LPMSN-laden DCLs soaked at pH 6.5 exhibit better drug loading than reference DCLs due to their specific adsorption. The sustained and extended release of glaucoma drugs by LPMSN-laden DCLs was successfully monitored in ALF, and the drug release mechanism was further explained. We also evaluated the cytotoxicity of LPMSN-laden DCLs, and qualitative and quantitative results showed no cytotoxicity. Our experimental results demonstrate that LPMSNs are excellent nanocarriers that have the potential to be used as safe and stable nanocarriers for the delivery of glaucoma drugs or other drugs. pH-triggered LPMSN-laden DCLs can significantly improve drug loading efficiency and control prolonged drug release, indicating that they have great potential for future biomedical applications.

Hydrogel Contact Lenses Embedded with Amine-Functionalized Large-Pore Mesoporous Silica Nanoparticles with Extended Hyaluronic Acid Release.

Contact lenses (CLs) have emerged as an effective method for delivering ophthalmic drugs. In this research, we designed hydrogel CLs capable of extended release, utilizing large-pore mesoporous silica nanoparticles (LPMSNs) to deliver hyaluronic acid (HA) for treating dry eye syndrome. LPMSNs were functionalized with amine groups (LPMSN-amine) to enhance HA loading and release capacity. In vitro release studies demonstrated that LPMSN-amine CLs exhibited superior slower HA release than LPMSN-siloxane and standard CLs. Within 120 h, the cumulative amount of HA released from LPMSN-amine CLs reached approximately 275.58 µg, marking a 12.6-fold improvement compared to standard CLs, when loaded from 0.1 wt% HA solutions. Furthermore, LPMSN-amine CLs effectively maintained moisture, mitigating ocular surface dehydration, making them a promising solution for dry eye management. This study successfully developed LPMSN-amine CLs for extended HA release, identifying the optimal functional groups and loading conditions to achieve sustained release.

Enhanced Luminous Efficacy and Stability of InP/ZnSeS/ZnS Quantum Dot-Embedded SBA-15 Mesoporous Particles for White Light-Emitting Diodes.

Environmentally friendly quantum dots (QDs) of InP-based materials are widely investigated, but their reliability remains inadequate to realize their full potential and wide application. In this study, InP/ZnSeS/ZnS QDs (pristine QDs) were dispersed and embedded into Santa Barbara Amorphous-15 mesoporous particles (SBA-15 MPs) for the first time. A solvent-free method for preparing QD white light-emitting diodes (WLEDs) that is compatible with the WLED packaging process was developed. The photoluminescence (PL) spectrum of pristine QD powder exhibited cluster states and had huge redshift of approximately 23 nm. By comparison, the PL spectrum of the SBA-15 MP/QD hybrid powder had a slight redshift of approximately 8 nm, only because the pristine QDs were dispersed and embedded well in the SBA-15 MPs. The PL intensity of the SBA-15 MP/QD hybrid powder slightly decreased after heating and cooling compared with that of the pristine QDs. Moreover, the luminous efficacy of the SBA-15 MP/QD hybrid WLEDs was enhanced by approximately 14% compared with that of the pristine QD-WLEDs. Furthermore, reliability analysis revealed that the SBA-15 MPs could improve the stability of the pristine QDs on chips. Thus, these MPs promise good potential for applications in mini-LEDs in the future.

Far-field of GaN film-transferred green light-emitting diodes with two-dimensional photonic crystals.

Far-field distributions of GaN-based photonic crystal (PhC) film-transferred light-emitting diodes (FT-LEDs) were investigated. The thickness of the device is about 840 nm. The emission wavelength is around 520 nm. The PhC region is a square lattice with a/lambda around 0.5. Angular-resolved measurements in the Gamma-X and Gamma-M directions were made in the polarized-resolved manner. Guided mode extraction behavior in agreement with the two-dimensional free-photon band calculation was observed. In addition, the pseudo-TM behavior for the non-collinearly coupled modes was observed. The azimuthal-mapping of the angular-resolved spectra revealed the evolution of the collinearly and the non-collinearly coupled modes. Furthermore, the light enhancement of approximately 2.7x and the collimation angle about 102.3 degrees were achieved.

Correction: Preparation of a colloidal photonic crystal containing CuO nanoparticles with tunable structural colors.

[This corrects the article DOI: 10.1039/C5RA21035F.].

Anisotropy of light extraction from GaN two-dimensional photonic crystals.

Angular distribution of light diffracted out of the plane of two-dimensional photonic crystals (PhC) has been studied in the azimuthal direction with a specially designed waveguide structure. The optical images of the light extraction patterns from the guided photoluminescence light are obtained with laser excitation in the center of the annual structure made on GaN multilayer. For increasing lattice constant, symmetric patterns with varying number of petals according to the symmetry of the PhC are observed. The appearance and disappearance of the petals can be explained using the Ewald construction in the reciprocal space. The dependence of light extraction on the lattice constant and orientation, and incident angle are investigated.

High-performance quantum dot light-emitting diodes using chip-scale package structures with high reliability and wide color gamut for backlight displays.

High reliability and wide color gamut light-emitting diodes (LEDs) that use composite quantum dot films (CQDFs) protected by chip-scale package (CSP) structures are presented. CQDFs containing CdZnSeS/ZnS core-shell QDs and the K2SiF6:Mn4+ phosphors were mixed with silicone gel and used as color converters in the CSP QD-LEDs. The CSP QD-LEDs, used for backlight displays, transmitted through a color filter and exhibited ITU-R Recommendation BT.2020 of approximately 86% (a National Television System Committee value of 115%). Furthermore, we performed a long-term reliability analysis test on the CSP QD-LEDs for 2352 h to verify whether the optical performance of CSP QD-LEDs does not significantly degrade relative to that of a conventional plastic leaded chip carrier QD-LEDs. We implemented a highly reliable package technology that can protect the QDs, solve the moisture/oxygen problems in defective QD-LEDs, and produce a backlight source for display with a wide color gamut.

High-Efficiency Robust Free-Standing Composited Phosphor Films with 2D and 3D Nanostructures for High-Power Remote White LEDs.

This study demonstrated that combined free-standing quasi-amorphous/micropattern (QA/MP) composited resin film-assisted phosphor films enhanced the mechanical robustness, luminous efficacy, color rendering index (CRI), and special R9 of high-power remote warm white light-emitting diodes (WLEDs). Introducing QA/MP nanostructures into phosphor film resulted in high efficiency of remote warm WLEDs with low phosphor thickness (approximately 25 µm) and reduced the correlated color temperature (CCT) from cold white light (approximately 5565 K) to warm white light (approximately 3178 K). The QA/MP composited phosphor films (CPFs) used for high-power remote WLEDs enhanced the CRI and special R9 and reduced the CCT. These results were attributed to that QA resin film reflected the blue light and re-emitted the added red emission. CIR (84), a natural warm white CCT (3178 K), and an acceptable luminous efficacy (102.5 lm/W) were achieved from the QA/MP CPFs of high-power remote WLEDs during operation at an input power of 10 W (current of 700 mA). The bending strength of QA/MP CPFs at approximately 112 N was significantly enhanced by 40% compared with that of flat CPFs. The QA/MP CPFs applied to high-power remote WLEDs exhibited good thermal and optical stability. QA/MP CPFs were also conducted to a reliability analysis (RA), in which temperature of 85 °C and relative humidity of 85% were applied for 3288 h. Lumen maintenance was degraded by 8% during RA test because the transmittance of trimethylolopropane ethoxylate triacrylate resins was degraded under high temperature. Overall, we implemented a reliable and inexpensive technology that can potentially reduce phosphor thickness, address the out-bin problems of defective WLEDs, and fabricate flat-panel lighting source with good lighting quality.

InGaN Light-Emitting Diodes with an Embedded Nanoporous GaN Distributed Bragg Reflectors.

InGaN light emitting diodes (LED) structure with an embedded 1/4λ-stack nanoporous-GaN/undoped-GaN distributed Bragg reflectors (DBR) structure have been demonstrated. Si-heavily doped GaN epitaxial layers (n(+)-GaN) in the 12-period n(+)-GaN/u-GaN stack structure are transformed into low refractive index nanoporous GaN structure through the doping-selective electrochemical wet etching process. The central wavelength of the nanoporous DBR structure was located at 442.3 nm with a 57 nm linewidth and a 97.1% peak reflectivity. The effective cavity length (6.0λ), the effective penetration depth (278 nm) in the nanoporous DBR structure, and InGaN active layer matching to Fabry-Pérot mode order 12 were observed in the far-field photoluminescence radiative spectra. High electroluminescence emission intensity and line-width narrowing effect were measured in the DBR-LED compared with the non-treated LED structure. Non-linear emission intensity and line-width reducing effect, from 11.8 nm to 0.73 nm, were observed by increasing the laser excited power. Resonant cavity effect was observed in the InGaN LED with bottom nanoporous-DBR and top GaN/air interface.