A Ce(3+)-activated fluorosulfide phosphor (β-YFS:Ce(3+)) was synthesized by solid-state reaction in a sealed tube. The crystal structure has been refined from the XRD profiles and there are two different crystallographic rare earth sites, namely, Y(1) and Y(2), where the Ce(3+) ions occupied. The emission band with a maximum at 495 nm of β-Y(0.99)Ce(0.01)FS phosphor was characterized by the 4f-5d transitions of Ce(3+) ion. With increasing Ce(3+) concentration, the emission variations were observed from 495 to 547 nm. When β-YFS:Ce(3+) phosphors were utilized to incorporate with n-UV/blue chip, greenish-white light with color rendering index of 65-77 were obtained. The results indicate that the tunable green- to yellow-emitting β-YFS:Ce(3+) can serve as a potential phosphor for incorporation in fabrication for solid-state lighting. The preparation, spectroscopic characterization, quantum efficiency, thermal-quenching behavior, and related LED device data are also presented.
This study demonstrates a novel package design to store colloidal quantum dots in liquid format and integrate them with a standard LED. The high efficiency and high quality color performance at a neutral white correlated color temperature is demonstrated. The experimental results indicate that the liquid-type quantum dot white light-emitting diode (LQD WLED) is highly efficient and reliable. The luminous efficiency and color rendering index (CRI) of the LQD WLED can reach 271 lm Wop(-1) and 95, respectively. Moreover, a glass box is employed to prevent humidity and oxygen erosion. With this encapsulation design, our quantum dot box can survive over 1000 hours of storage time.
Abstract-This study investigates the effect of temperature on CdSe/ZnS quantum dots (QDs) in GaN-based light-emitting diodes (LEDs) using the phosphor conversion efficiency (PCE) and LED junction temperature. In our simulation, the blue chip and CdSe/ZnS QDs temperature are similar because of their minimal thickness. Furthermore, to verify the effect of temperature on CdSe/ZnS QDs, we use continuous wave and pulsed current sources to measure the relationship between the temperature and relative PCE. Higher junction temperatures are observed with greater CdSe/ZnS QD volume in LEDs. This is attributed to the thermal conduction and nonradiative energy between CdSe/ZnS QDs and blue chip. Therefore, if thermal management is improved, CdSe/ZnS QDs are expected to be used as color converting material in LEDs.Index Terms-Light-emitting diodes (LEDs), GaN, quantum dots (QDs), phosphor.
This study employs the polyfluorene composite (called Green B) with several colors of quantum dots to generate the highcolor-rendering index (CRI) white LEDs. The Green B polymer is a good candidate to manufacture the hybrid w-LED because of its good quantum efficacy. The hybrid w-LEDs are fabricated by the mixing of Green B with yellow quantum dots and red quantum dots or orange quantum dots to obtain the correlated color temperatures of 3500 and 5500 K. The use of the hybrid polymer/QDs w-LEDs is proved to be beneficial as QD w-LEDs can improve the CRI up to 90 in 3500 K. The luminous efficiency of such devices can be as high as 17.2l m/W.
Index Terms-Light-emitting diodes (LEDs), quantum dots (QDs).
In this study, a novel photoluminescent quantum dots device with laser-processed microscale patterns has been demonstrated to be used as a white light emitting source. The pulsed laser ablation technique was employed to directly fabricate microscale square holes with nano-ripple structures onto the sapphire substrate of a flip-chip blue light-emitting diode, confining sprayed quantum dots into well-defined areas and eliminating the coffee ring effect. The electroluminescence characterizations showed that the white light emission from the developed photoluminescent quantum-dot light-emitting diode exhibits stable emission at different driving currents. With a flexibility of controlling the quantum dots proportions in the patterned square holes, our developed white-light emitting source not only can be employed in the display applications with color triangle enlarged by 47% compared with the NTSC standard, but also provide the great potential in future lighting industry with the correlated color temperature continuously changed in a wide range.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.