Browsing by Subject "White light-emitting diodes"

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Ag@SiO2-embedded InGaN/GaN nanorod array white light-emitting diode with perovskite nanocrystal films
(Elsevier, 2021-10-28) Shin, Do-Y.; Kim, T.; Akyüz, Özgün; Demir, Hilmi Volkan; Lee, In-H.
White light-emitting diodes (LEDs) are great candidates for general lighting. Phosphors have commonly been used for the color conversion layers of white LEDs; however, they backscatter more than half of the down-converted light, which is lost within the device, thus degrading the overall performance. In this study, we propose and demonstrate white LEDs with improved efficiency enabled by the intimate integration of Ag@SiO2-supported blue InGaN/GaN nanorod LEDs together with green- and red-emitting perovskite nanocrystal (PNC) films as color conversion layers. The photoluminescence (PL) intensity of the blue LEDs (BLEDs) was significantly enhanced owing to the localized surface plasmon (LSP) effect of Ag@SiO2 nanoparticles. In addition, the perovskite PL intensity was improved by the high-power BLED backlight. The resulting PL intensity of the Ag@SiO2 nanoparticle-embedded nanorod white LED was 62% greater than that of a planar white LED.
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Spectrally tunable white light-emitting diodes based on carbon quantum dot-doped poly(N-vinylcarbazole) composites
(American Chemical Society, 2024-01-26) Sahin Tiras, Kevser; Biçer, Aysenur; Soheyli, Ehsan; Mutlugün, Evren
Electroluminescent white light-emitting diodes (WLEDs) are always of great interest for emerging display applications. Carbon-based quantum dots (CQDs) are the newest emerging nanoscale materials that can be employed for this purpose, owing to their broad and bright light emission properties. In the present work, highly luminescent CQDs with an emission quantum yield of 60% were prepared via a colloidal solvothermal method and subsequent silica gel column chromatography. The photoluminescence (PL) peak was located at 550 nm possessing yellow emission, with a full width at half-maximum of 98 nm and a relatively long lifetime of 10.23 ns through a single-exponential recombination pathway. CQDs were employed in an electroluminescent device architecture of an ITO/PEDOT:PSS/TFB/CQD:PVK/TPBi/LiF/Al structure and blended with poly(N-vinylcarbazole) (PVK) to evaluate their ability to reach white electroluminescent emission. Results confirmed a high external quantum efficiency (EQE) of 0.76% and a maximum luminescence of 774.3 cd·m-2. Tuning the ratio between CQDs and PVK from 1:10.25 to 1:5.75 resulted in a systematic shift in CIE x-y coordinates from 0.23-0.26 to 0.21-0.24, located close to the cool white region. The results of the present study can be considered a step forward in fabricating efficient WLEDs based on low-cost CQDs.