We use organic cations to template the solution-state assembly of corrugated lead halide layers in bulk crystalline materials. These layered hybrids emit radiation across the entire visible spectrum upon ultraviolet excitation. They are promising as single-source white-light phosphors for use with ultraviolet light-emitting diodes in solid-state lighting devices. The broadband emission provides high color rendition and the chromaticity coordinates of the emission can be tuned through halide substitution. We have isolated materials that emit the "warm" white light sought for many indoor lighting applications as well as "cold" white light that approximates the visible region of the solar spectrum. Material syntheses are inexpensive and scalable and binding agents are not required for film deposition, eliminating problems of binder photodegradation. These well-defined and tunable structures provide a flexible platform for studying the rare phenomenon of intrinsic broadband emission from bulk materials.

/pdf/self-assembly-of-broadband-white-light-emitters-32y2hwzxoq.pdf

Self-assembly of broadband white-light emitters.

Currently, the major commercial white light-emitting diode (WLED) is the phosphor-converted LED made of the InGaN blue-emitting chip and the Ce3+:Y3Al5O12 (Ce:YAG) yellow phosphor dispersed in organic epoxy resin or silicone. However, the organic binder in high-power WLED may age easily and turn yellow due to the accumulated heat emitted from the chip, which adversely affects the WLED properties such as luminous efficacy and color coordination, and therefore reduces its long-term reliability as well as lifetime. Herein, an innovative luminescent material: transparent Ce:YAG phosphor-in-glass (PiG) inorganic color converter, is developed to replace the conventional resin/silicone-based phosphor converter for the construction of high-power WLED. The PiG-based WLED exhibits not only excellent heat-resistance and humidity-resistance characteristics, but also superior optical performances with a luminous efficacy of 124 lm/W, a correlated color temperature of 6674 K and a color rendering index of 70. This easy fabrication, low-cost and long-lifetime WLED is expected to be a new-generation indoor/outdoor high-power lighting source.

A new-generation color converter for high-power white LED: transparent Ce3+:YAG phosphor-in-glass

Transparent ceramics: Processing, materials and applications

The development of nonlinear optical (NLO) borate crystals for generation of visible and UV light is reviewed. We first discussed on the basic principles of laser frequency conversion. Then, we examine the trends in research on NLO crystals. The background and present status of NLO borate crystals are summarized. The main considerations are focused on the discussion of crystals like CsLiB6O10 (CLBO), GdxY1−xCa4O(BO3)3 (GdYCOB) and K2Al2B2O7 (KAB). Properties of related materials like β-BaB2O2 (BBO), LiB3O5 (LBO), KBe2BO3F2 (KBBF), Sr2Be2BO7 (SBBO), CsB3O5 (CBO), GdCa4O(BO3)3 (GdCOB) and YCa4O(BO3)3 (YCOB) are included for comparison. We aim to provide a complete view of developing a new NLO borate material for actual laser applications. This review covers various aspects including the search for new materials, the growth of bulk crystals, the characterization of crystal properties as well as the development of new techniques to overcome obstacles in actual laser application, namely, thermal dephasing and laser-induced damage. Finally, perspectives on NLO borate crystals and all-solid-state UV lasers are evaluated.

Recent development of nonlinear optical borate crystals: key materials for generation of visible and UV light

The wavelength down conversion approach to solid-state lighting (SSL) uses down conversion materials to produce visible light when excited by near-UV or blue emission from InGaN LEDs. This review discusses two classes of down conversion materials: phosphors and semiconductor quantum dots (QDs). Strong absorption of the excitation wavelength; high luminous efficacy of radiation, which enables white light with a high color rendering index and a low correlated color temperature; high quantum efficiency; and thermal and chemical stability are some of the criteria for down converters used in SSL. This review addresses the challenges in the development of down converters that satisfy all these criteria. We will discuss the advantages and disadvantages of several phosphor compositions for blue and near-UV LEDs. The use of core/shell architectures to improve the photoluminescence and moisture resistance of phosphors is presented. QDs are another class of down conversion materials for near-UV and blue LEDs. Strategies to improve the photostability and reduce the thermal quenching of QDs include strain-graded core/shell interfaces and alloying. We discuss Cd-containing II–VI QDs, and Cd-free III–V and I–III–VI QDs and their potential for SSL applications. Finally, a description of different methods to integrate the phosphors and QDs with the LED is given.

Review: Down Conversion Materials for Solid‐State Lighting

Properties of transparent Ce:YAG ceramic phosphors for white LED

Optical properties of rapidly grown KDP crystal improved by thermal conditioning

Rapid growth over 50 mm/day of water-soluble KDP crystal

Growth and characterization of deuterated L-arginine phosphate monohydrate, a new nonlinear crystal, for efficient harmonic generation of fusion experiment lasers

Transparent Ce:YAG ceramics were synthesized from the Ce:YAG powder which was produced by co-preparation method of the hydroxides. The Ce:YAG ceramics exhibit a broad emission band peaked at 530 nm due to the 5d 4f transition of Ce 3+ . The transmittances of the samples obtained were 70 ~ 87 % at 800 nm. The absorption coefficient and emission intensity of Ce 3+ were increased with the increase of the thickness. With increasing thickness of the sample, the color coordinates of the Ce:YAG ceramics under 465 nm LED excitation shifted from the blue region to the yellow region with passing nearby the theoretical white point. The highest value of luminous efficacy of the white LED was 73.5 lm/W.

https://iopscience.iop.org/article/10.1088/1757-8981/1/1/012031/pdf

Kana Fujioka

Papers

Properties of transparent Ce:YAG ceramic phosphors for white LED

Optical properties of rapidly grown KDP crystal improved by thermal conditioning

Rapid growth over 50 mm/day of water-soluble KDP crystal

Growth and characterization of deuterated L-arginine phosphate monohydrate, a new nonlinear crystal, for efficient harmonic generation of fusion experiment lasers

Preparation and Optical Properties of Transparent Ce:YAG Ceramics for High Power White LED