The development of full-spectrum phosphors is the key to the next generation of high-quality light-emitting devices. Researchers from Finica University in Vietnam reported a new broadband phosphor based on a single-component aluminum-doped zinc oxide phosphor. Under the excitation of 325 nm ultraviolet light, the ZnO:Al phosphor has a full-spectrum emission in the visible light band from 400 to 800 nm. The CIE chromaticity coordinates are (0.42, 0.48), the quantum efficiency is 43%, and the color rendering index (CRI) It is 74, the correlated color temperature (CCT) is 3873 K, and the activation energy is 0.22 eV. Only with this broadband luminescent aluminum-doped zinc oxide phosphor, an emission spectrum with a high CRI of 87 and a CCT of 4067k can be obtained. The results show that the single-component Al3+ single-doped warm white phosphor is an excellent candidate material for white light devices. Related papers were published in the journal Dalton Transactions with the title "Single-composition Al3+-singly doped ZnO phosphors for UV-pumped warm white light-emitting diode applications".
Due to its small size, long life, high energy efficiency, fast response time, energy saving and environmental protection, white light emitting diodes (WLEDs) are gradually replacing traditional light sources such as incandescent lamps, fluorescent lamps (FL) or high pressure sodium lamps (HPS). As we all know, the quality of light is characterized by several key figures of merit, including correlated color temperature (CCT), luminous efficiency (LE) and color rendering index (CRI). Among them, CRI is a key parameter of full-color display WLED, CRI can be changed from 0 to 100; among them, a higher CRI value means better reproduction of accurate colors.
In recent years, a new term "full visible spectrum lighting" has been widely used worldwide. It proposes a high CRI light source that can simulate natural light. Generally, commercial WLEDs are manufactured by coating yellow phosphors (YAG: Ce3+) on blue LED chips; however, due to the lack of red components in the visible area, it has low CCT and poor CRI. To overcome these problems, one feasible method is to use UV-LED chips coated with blue (B), green (G), and red (R) phosphors. However, due to the reabsorption of blue light by the red and green phosphors, the obtained WLED shows relatively low luminous efficiency.
Therefore, the development of full visible light is of great significance. Zinc oxide (ZnO) has a large band gap of 3.3-3.4eV, and the exciton binding energy is as high as 60 meV at room temperature. It can emit light in the entire ultraviolet/visible region and is expected to be widely used in photovoltaic devices such as solar cells and photoanodes. It is also reported that metal-doped ZnO-based materials such as Mg-doped ZnO films, Ga-doped ZnO nanorods and Al and Mn-doped ZnO nanopowders can obtain broadband white spectra. However, micron-sized particles generally require phosphors for manufacturing next-generation light-emitting devices with better light quality. Therefore, the full-visible spectrum single-phase zinc oxide-based phosphor is expected to be used to prepare environmentally friendly WLEDs with high efficiency and high CRI.
