Producing white light using near-UV LEDs requires the development of new phosphors, as well as the modification of certain existing ones. In this review, we discuss the luminescent properties of potential phosphors: oxides, silicates, phosphates and nitrides. We evaluate phosphors that employ 4f-5d transitions, line emission, the use of sensitizers and transition metal elements. We include information on the optical transitions and how these can limit the selection of a composition.

During the past few years there has been a significant progress in adapting the properties of non-Cd quantum dots (QDs) for lighting applications. It includes synthesis of novel materials, improvement of quantum efficiency and thermal stability, and most importantly, manufacturability on a scale large enough to meet the needs of the lighting industry. In this paper, we review the characteristics of three most mature non-Cd QD material systems, InP, CuInS2 and doped ZnS/ZnSe, from the perspective of lighting applications. Of these three systems, the InP-based QDs with core/shell structure are now available with quantum efficiency (QE) comparable to the best performing CdSe QDs, and in quantities large enough to meet the lighting needs. The CuInS2 QDs have also emerged as another non-toxic alternative to CdSe QDs but they need significant development to be comparable to InP and CdSe QDs.

No abstract

No abstract

Using the proper synthesis technique is an important consideration in the development of phosphors for white light emission from near UV LEDs (emission in the range 380 nm – 410 nm). In this review, synthesis methods are analyzed and compared, with the goal of obtaining the optimal particle size, morphology and purity. Post-synthesis treatments such as the fabrication of core/shell particles as well as annealing conditions are discussed. Finally, methods to incorporate phosphors with the diode are discussed, with an emphasis on electrophoretic deposition.

With more and more research efforts being focused on phosphors for LEDs, new systems are constantly being explored. One such system is the ABPO4:Eu2+ with A = Li, Na and K and where B = Ca, Sr, and Ba. These phosphors will produce varying blue emissions from 400 nm out to around 480 nm upon excitation by UV emitting LED sources. In this study we have explored nine different phosphors having different combinations of A and B. The spectroscopic properties of these phosphors, as well as their external quantum efficiencies, and their temperature dependant lifetimes will be discussed.

Electrophoretic deposition (EPD) is a method to deposit particles dispersed in a liquid onto a substrate under the force of an applied electric field, and has been applied for depositing phosphors for application in solid state lighting. The objective is to deposit phosphors in a “remote phosphor” configuration for a UV-LED-based light source for improved white light extraction efficiency. It is demonstrated that EPD can be used to deposit red-, green-, blue-, yellow- and orange-emitting phosphors to generate white light using a near UV-emitting LED by either depositing a phosphor blend or sequentially individual phosphor compositions.

Electrophoretic deposition (EPD) has been used for phosphor screening for a variety of emissive information displays and more recently, for solid state lighting. EPD is well suited to deposit the fine (nanometer to micrometer diameter) phosphor particles needed for high resolution displays. The fundamentals of the EPD process in an isopropanol (IPA) bath have been characterized by the dissociation behavior of nitrate salts in IPA, measurement of the effects of pH and nitrate salt concentration on the zeta potential of the particles, studying of the processing conditions and modeling of the deposition rates. The electrochemical precipitation reactions form an adhesive agent for the particles and the adhesion strength can be enhanced by various methods to meet the requirements of these technologies.