Applying InP/ZnS Green-Emitting Quantum Dots and InP/ZnSe/ZnS Red-Emitting Quantum Dots to Prepare WLED With Enhanced Photoluminescence Performances

Abstract

Based on blue LED chips to excite Ce-doped yttrium aluminum garnet (YAG: Ce 3+) yellow phosphors, InP/ZnS green-emitting quantum dots (QDs) and InP/ZnSe/ZnS red-emitting QDs are used as light conversion materials for WLEDs to improve the color rendering index (CRI) of the device and improve its color coordinates. We have proven this in previous work. But in the previous work, we only studied the CRI of the driving current from 5 mA to 100 mA. The CRI and the Commission International de L'Eclairage (CIE) chromaticity coordinates of the WLED device prepared before is not ideal under high current conditions. The emission peak position of InP/ZnSe/ZnS red-emitting QDs we used in previous work is 605nm. In this article, we adjusted the emission peak position of InP/ZnSe/ZnS red-emitting QDs to 611nm, and prepared WLED in the same way, which improved the problem that the CRI of WLED devices decreases rapidly and the chromaticity coordinates change greatly under high current conditions. The CRI of prepared WLED device in this article was increased to 91.0, the CIE chromaticity coordinates is (0.3365, 0.3334), and the correlated color temperature (CCT) is 5313 K. We also tested the dependence of the electroluminescence (EL) spectrum, CRI, CCT and chromaticity coordinates of the prepared WLED device on the current. Compared with the prepared WLED device before, the CRI of the WLED device prepared in this article has always remained above 90, hovering between 90 ~ 91, very stable. The chromaticity coordinate distribution is also very concentrated, the amplitude of the offset black body radiation is small, and it shows excellent color rendering and stable working performance. A 30-day aging test was performed on the prepared WLED device.

Measurement of the Effect of Luminescent Layer Parameters on Light and Communication Properties

“…The process of luminescent layer production was directed so that after the optimisation of the luminescent layer parameters, the generated light would fall within this narrowly defined region and in the vicinity of Illuminant E, which is the point of spectral equilibrium in the CIE 1931 colour diagram. Indeed, light with a location in the vicinity of Illuminant E is known to have CCT values corresponding to daylight white light and high CRI values [8], [9], [32], [33]. These are therefore desirable colorimetric parameters suitable even for demanding lighting applications.…”

“…At the same time, according to this standard, a CCT in the range 4000-6500 K is required for several types of workplaces. In doing so, it is known that within the CIE 1931 colour chart, light with the required CRI and CCT values is in the vicinity of Illuminant E [8], [9], [32], [33]. Therefore, the optimization process for the production of luminescence samples was conducted in such a way that the CIEx,y 1931 color coordinates of the light generated by the luminescence layers were as close to Illuminant E as possible.…”

“…For example, the authors of [8] used red light-emitting carbon dots (R-CDs), combining a blue chip, a YAG:Ce phosphor and R-CDs to create a WLED with a CRI = 90.9 at colour coordinates CIE x,y = (0.344; 0.333). The use of InP/ZnS Green-Emitting and InP/ZnSe/ZnS Red-Emitting Quantum Dots in combination with a blue chip and a YAG:Ce phosphor is presented in [9], and the WLED prepared in this way exhibited CRI = 91 and CCT = 5313 K for colour coordinates (0.3365; 0.3334).…”

Quantum dots printing paste for display backlights: Preparation, characterization, and applications

“…In recent years, quantum dots (QDs) have attracted wide attention due to their adjustable wavelength, high color purity, and quantum efficiency, which have been successfully applied in display fields 1–3 . At present, researches on QDs for display applications mainly include two aspects: electroluminescence (EL) technology 4–6 and photoluminescence (PL) technology 7–9 .…”

“…In recent years, quantum dots (QDs) have attracted wide attention due to their adjustable wavelength, high color purity, and quantum efficiency, which have been successfully applied in display fields. [1][2][3] At present, researches on QDs for display applications mainly include two aspects: electroluminescence (EL) technology [4][5][6] and photoluminescence (PL) technology. [7][8][9] Combining QDs luminescent materials with matrix materials to form new composite luminescent materials has been the focus of researchers in the scientific and industrial communities, and it is also the key to the application of QDs in liquid crystal display backlights.…”