Bismuth‐activated, narrow‐band, cyan garnet phosphor Ca₃Y₂Ge₃O₁₂:Bi³⁺ for near‐ultraviolet‐pumped white LED application

Abstract

Herein, a novel Bi 3+ -activated Ca 3 Y 2 Ge 3 O 12 (CYGO) narrow-band cyan-emitting phosphor was synthesized. It can be excited from 320-420 nm, and the strongest excitation peak is located at 370 nm, which is suitable for current near-ultraviolet (NUV) chips perfectly. The full width at half maximum is at 52 nm. By analyzing the crystal structure of the sample, we infer that the Bi 3+ ions replace the Y 3+ site to form a highly symmetrical BiO 6 octahedron. The time-resolved photoluminescence (TRPL) spectra of CYGO: Bi 3+ reveal that the only a single emission center exists in the host lattice. A warm white light-emitting diode (WLED) device with a low correlated color temperature (3148 K) and a high color rendering index (90.2) was fabricated by using the as-prepared sample, and the significant thermal stability of CYGO: Bi 3+ guarantees its potential application in WLEDs. It is verified that the structure with only one crystallographic Y site for Bi 3+ dopant occupation and highly symmetrical and dense structure is conducive to realize narrow-band emission, which will provide experience for researchers to explore more Bi 3+ -activated phosphors used for high-end lighting.

Insights into blue-light activated red-emitting persistent luminescence from Pr3+-doped phosphors

“…The band gap can be calculated using the following equations:( αhv ) n = A ( hv − E g )where α is the absorption coefficient, hv is the incident photo energy, A is a constant, and n = 1/2 for an indirect band gap or 2 for a direct band gap and in this case, the value of n is 2. 35,36 As a result, by the extrapolation of α = 0, the band gap of CCGGO is estimated to be approximately 4.03 eV, as presented in Fig. 3b.…”

Investigation on the luminescence properties and mechanism of a novel Pr3+-based red persistent luminescence phosphor Cd3Ga2Ge3O12:Pr3+

“…36,37 We can estimate the band gap by using the equation as follows:( αhv ) 2 = A ( hv − E g ) α = (1 − R 2 )/2 R Here α is the absorption coefficient, hν equals the incident photon energy, A is a constant, E g is the optical band gap, and R is the observed absorption rate in the absorption spectra. 36,37 From Fig. 5(b), the band gaps of CGGO and CGGO:0.0015Pr 3+ are calculated to be approximately 3.68 and 3.75 eV, respectively.…”

“…Here a is the absorption coefficient, hn equals the incident photon energy, A is a constant, E g is the optical band gap, and R is the observed absorption rate in the absorption spectra. 36,37 From Fig. 5(b), the band gaps of CGGO and CGGO:0.0015Pr 3+ are calculated to be approximately 3.68 and 3.75 eV, respectively.…”

Tunable ultra-broadband full-visible-spectral emission of Bi3+-doped aluminate phosphors enabled by structure transformation and site occupancy engineering

“…20,21 Moreover, the absorption of Bi 3+ usually occurs in the UV region, where the spectral re-absorption can be well restrained, making it a suitable activator for UV-WLEDs. 22,23 Recently, many researchers have achieved broad-band emission from Bi 3+ by altering its coordination environment within the crystal field. For example, Kang et al achieved whole visible spectrum emission in YNbO 4 by substituting Nb 5+ with V 5+ and replacing Y 3+ with Sc 3+ ions.…”