In this paper, we present an innovative top-down approach for fabricating billions of InGaN/GaN-based dot-Light-Emitting Diodes (LEDs) that eliminate the need for a sacrificial layer. Our method combines Electrochemical Etching (ECE) and sonochemical separation to isolate the dot-LEDs. Key electrochemical parameters are investigated to assess their impact on the nanopore size, separation efficiency, and the dot-LEDs’ emission properties. Higher voltages result in more extensive electrochemical etching of the n-GaN portion. Furthermore, lower vapor pressures, along with higher viscosities and surface tension, enhance the sonochemical separation efficiency of dot-LEDs during the ECE process. Blue electroluminescent devices fabricated using these dot-LEDs achieved an External Quantum Efficiency (EQE) of 7.34% at a forward voltage of 4.2 V, with remarkable luminance efficacy. Although the current generation of blue Au-coated dot-LEDs does not surpass the EQE of existing displays, it marks a significant step in the burgeoning field of dot-LED display technology.
This study introduces quantum dot (QD)-based polarized white light-emitting diodes (W-LEDs) combined with a shortwavelength pass dichroic filter (SPDF), which transmit blue wavelength regions and reflect yellow wavelength regions, and a reflective polarizer film (RPF)-sandwiched AgIn5S8-ZnS QD layer using an electrospray (e-spray) method. The AgIn5S8-ZnS QDs are good candidates for W-LEDs because of their broad emission band (~100 nm) from the donoracceptor emission. The yellow emitting AgIn5S8-ZnS QDs are synthesized using a colloidal hot injection method and mixed with dimethylformamide (DMF), toluene, and poly(methyl methacrylate) (PMMA) for e-spray coating on glass. Furthermore, SPDFs are used instead of glass substrates to enhance the yellow emission from the QD layer. To create the polarized light, the RPF is fabricated on QD-coated glass and SPDFs. To create white light, a blue LED chip (λmax = 450 nm) is used as the blue light source and an excitation source for the yellow QD film with an applied current of 60 mA. The electroluminescence (EL) intensity with an angular orientation of the polarizer is measured as a function of the polarizer-rotating angle from −90° to 90° at 10° intervals.
In this study, several combinations of multi-package white light-emitting diodes (LEDs), which combine an InGaN blue
LED with green, amber, and red phosphor-converted LEDs (pc-LEDs), were characterized by changing the peak
wavelength of green pc-LEDs between 515nm and 560nm (515, 521, 530, 540, 550, 560nm) in color temperature of
6,500K and 3,500K. Various green monochromatic pc-LEDs were fabricated by capping a long-wave pass-filter (LWPF)
on top of pc-LEDs to improve luminous efficacy and color purity. LWPF-capped green monochromatic pc-LED can
address the drawback of green semiconductor-type III-V LED, such as low luminous efficacy in the region of green gap
wavelength. Luminous efficacy and color rendering index (CRI) of multi-package white LEDs are compared with
changing the driving current of individual LED in various multi-package white LEDs. This study provides a best
combination of four-color multi-package white LEDs which has high luminous efficacy and good CRI.
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