Bright cyan-emitting phosphor is indispensable to fill the cyan gap for the fabrication of full-visible-spectrum warm-white light-emitting diodes (LEDs) with high color rendering index (CRI). In this study, we demonstrate a novel efficient cyan-emitting Ce 3+ -activated CaLu 2 HfScAl 3 O 12 (CLHSA) garnet phosphor for application in blue-light-excited full-spectrum warm-white LEDs. CLHSA:Ce 3+ phosphors show broadband excitation spectra in the 300–470 nm spectral range with a maximum peak at 408 nm, indicating they can be efficiently pumped by the blue LED chips. The optimal doping concentration of Ce 3+ ions is found to be 1 mol%. Upon 408 nm excitation, the optimal CLHSA:1%Ce 3+ phosphor gives rise to a bright broadband cyan emission (peak position: 498 nm; bandwidth: 97.5 nm) with CIE chromaticity coordinates of (0.2196, 0.4265) and high photoluminescence quantum yield of 64.5%. Finally, we have fabricated a blue-light-excited high-CRI warm-white LED device by employing the CLHSA:1%Ce 3+ cyan phosphor, commercial YAG:Ce 3+ yellow phosphor and commercial CaAlSiN 3 :Eu 2+ red phosphor as well as a 450 nm LED chip, which demonstrates a bright warm-white light emission with a high CRI (Ra = 92.6), a low correlated color temperature (3660 K), and good CIE chromaticity coordinates of (0.3993, 0.3939) as well as a high luminous efficacy of 45 lmW −1 . Therefore, this newly discovered efficient cyan-emitting CLHSA:1%Ce 3+ phosphor is promising for application in blue-chip-pumped full-visible-spectrum warm-white LEDs with high CRI values.
The emission of cyan light (470–500 nm), an essential component of the visible light spectrum, plays a crucial role in lighting, display, and light communication. CsPbBr3 quantum dots (QDs) have shown excellent performance in the green spectral regions, with high color purity, efficiency, and brightness. In order to shift the emission wavelength to the cyan, mixed-halide compositions and quantum-confinement engineering have been employed. Unfortunately, mixed-halide perovskites exhibit undesirable phase separation during optical and electrical excitations, leading to spectral instability. Quantum confinement in pure-halide QDs requires synthetic protocols that involve high loading of long-chain insulating ligands. In this study, we report color-stable cyan CsPbBr3 quantum dots (C-PQDs) by surface passivation via incorporating Zn2+ cations. The incorporation of ZnBr2 into the precursor solution facilitates Zn2+ and Br− substitution into the QDs surface/subsurface layers to induce passivation of existing Pb2+ and Br− vacancies and increase the photoluminescence quantum yield from 53.6% to 96.4% at 480 nm. Moreover, after storage under ambient conditions for 30 days or exposure to ultraviolet light for 60 minutes or heating at 333 K, the PL intensity of ZnBr2-treated C-PQDs only shows a minimal decrease. Furthermore, white and cyan light-emitting diodes (LEDs) are successfully constructed, suggesting that the proposed ZnBr2-treated strategy can promote the development of perovskite materials for a wider range of optoelectronic applications.
Due to the complicated production process and reabsorption problem, the development and application for white light-emitting diodes (WLEDs) are affected. A combination of cyan and red phosphors with near-ultraviolet (n-UV) LED chip has been proposed to solve these problems. Its key is developing cyan phosphor with broad emission band and excellent performances. In this work, we have developed a broadband cyan-emitting phosphor RbBa 2 (PO 3 ) 5 : Eu 2+ (RBP: Eu 2+ ) by a solid-state method. The phase purity, crystal structure, luminescence properties and their relationship were investigated systematically. The RBP: Eu 2+ phosphor can yield asymmetric broadband cyan emission upon 350 nm light excitation , which is ascribed to the occupation of Eu 2+ for both the Ba1 and Ba2 sites. The measurement of temperature-dependent luminescence implies that the phosphor remains 89.5% of the initial value at 150 °C, which is much better than the commercial Ba 2 SiO 4 : Eu 2+ phosphor. Furthermore, a WLED device has been obtained by composing the RBP: 0.01Eu 2+ and CaAlSiN 3 : Eu 2+ phosphors with a 365 nm LED chip. The emitted white light can show fabulous performances with the color coordinates of (0.3792, 0.3359), correlated color temperature of 3841 K and CRI of 90.8. The results suggest the RBP: Eu 2+ phosphor to be a promising candidate for high-power WLEDs.
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