Optical Properties and Reliability Studies of Gradient Alloyed Green Emitting (CdSe)_x(ZnS)_1–x and Red Emitting (CuInS₂)_x(ZnS)_1–x Quantum Dots for White Light-Emitting Diodes

Abstract

Luminescent materials become one of interesting issues for white LED-based lighting devices (WLEDs) due to their high performances for converting the monochromatic light from UV/blue LED chips into white light. Nevertheless, the availability of rare earth materials, the low color rendering index (CRI) and too-cold color temperature of the white LEDs remain some drawbacks to penetrate into the general LED lighting markets. Herein, we report the development of rare-earth-free luminescent nanocomposites combined with a UV/blue LED chip in order to provide white light. Gradient alloyed cadmium selenide/zinc sulfide (CdSe) x (ZnS)1–x and copper indium sulfide/zinc sulfide (CuInS2) x (ZnS)1–x quantum dots have been used to achieve the luminescent nanocomposite films in silicone as polymer matrix. The optical performances were investigated upon LED excitation. The photometric parameters of systems consisting of luminescent nanocomposites and LEDs including color rendering index (CRI), correlated color temperature (CCT), Commission Internationale de l’Eclairage (CIE) chromaticity coordinates, and luminous efficacy can be tuned by controlling the compositions and thickness of nanocomposite films. Furthermore, the thermal stability and the reliability of these luminescent nanocomposite films were investigated.

An Efficient Synthesis and Photoelectric Properties of Green Carbon Quantum Dots with High Fluorescent Quantum Yield

“…The colour coordinates of white LEDs are (0.45, 0.37), the colour rendering index (CRI) is 87, and the CCT is 2520 K, which belongs to the warm white light area and is suitable for indoor lighting (Figure 9c). The warm white LEDs emitting bright warm light with high CRI were comparable to the white LEDs based on other CQDs, semiconductor QDs, and rare-earth phosphors in Table 5 [12,[35][36][37][38][39]. However, these articles did not take the PY of CQDs into consideration.…”

Optical Properties, Synthesis, and Potential Applications of Cu-Based Ternary or Quaternary Anisotropic Quantum Dots, Polytypic Nanocrystals, and Core/Shell Heterostructures

“…White light LEDs are an important class of LEDs aiming to produce emission as close as possible to blackbody emission at ≈ 6000 K, and therefore simulate sunlight to act as a replacement for a range of lighting sources used at present, including Cu–Sn-In–S based QDs [209] (Figure 17). A number of various Cu based QDs have also been demonstrated as promising white light sources [151,152,203,204,205,206,208,210,211,217,219,220,221,222], either via the use of down converting [152,203,204,205,206,207,208,209,210,219,220,221] or electroluminescence [211,217,218] s. These devices are achieved by either combining a number of luminescent sources or via the use of a single broad emission sources. Cu based QDs are an excellent fit for this type of light source due to the inherent broadness of the QD emission relative to other QDs.…”

Rare Earth‐Free Luminescent Materials for WLEDs: Recent Progress and Perspectives

“…[ 31 ] Rachod et al reported a rare‐earth white light‐emitting nanocomposite based on (CdSe) x (ZnS) 1− x /(CuInS 2 ) x (ZnS) 1− x QDs and silicone polymer, and made a systematic study on its optical properties and stability. [ 32 ] Xinsheng et al prepared light conversion films with high PLQY and used them in 405 nm near‐UV excited WLED devices by encapsulating blue, green, and red CdSe x S 1− x /ZnS QDs in ZIF‐8 MOFs. The encapsulation effectively suppressed concentration‐induced quenching, resulting in a high PLQY (86%), good thermal stability, and long‐term durability.…”