Green-Emitting Ca₆Sr₄(Si₂O₇)₃Cl₂: Eu²⁺Phosphors for White Light-Emitting Diodes

Abstract

A series of new green-emitting Ca6Sr4-xEux(Si2O7)3Cl2 phosphors were synthesized using the high-temperature solid-state reaction. Thermogravimetry-differential thermal analysis (TG-DTA) and X-ray diffraction (XRD) were used in order to determine the crystallization process and crystal structure of the obtained product. Complete optical studies including the diffuse reflection, photoluminescence excitation and emission measurements were performed. Crystallographic site-occupations of Eu2+ ions in the Ca6Sr4(Si2O7)3Cl2 host were assigned and two distinguishable Eu2+ sites, viz., Eu(1)2+ and Eu(2)2+, were confirmed. The luminescence natures of the Eu2+ emission, e. g., the Stokes shift and the concentration-dependent luminescence behaviors were also investigated in detail. Based on the experimental results and theoretical calculation, the dipole-dipole interaction was dominantly involved in the energy transfer from Eu(1)2+ to Eu(2)2+ ions, and the critical distance was determined to be about 14.69 Å. The thermal-quenching behaviors were further presented. In view of its strong absorption in the near-UV region, the intense green light emission peaking at 511 nm, as well as the lower thermal quenching, the Eu2+-doped Ca6Sr4(Si2O7)3Cl2 phosphor can serve as a potential new material for phosphor-converted light-emitting diodes (LEDs).

Blue–white–orange color-tunable luminescence of Ce3+/Mn2+-codoped NaCaBO3via energy transfer: potential single-phase white-light-emitting phosphors

“…Thus, the fundamental absorption edge (bandgap energy) of the NaCaBO 3 host was calculated to be approximately 4.48 eV by extrapolation, essentially due to the transition between the valence band and the conduction band in this host. 24 Obvious differences appear in the spectral profiles of Ce 3+ -doped and Ce 3+ /Mn 2+ -codoped samples compared to that of the NaCaBO 3 host. As the Ce 3+ ions are singly introduced into the NaCaBO 3 host, four absorption bands with maxima at 212, 252, 290, and 360 nm appears in the wavelength range of 200 to 450 nm, which is attributable to the transition from 4f 1 5d 0 to 4f 0 5d 1 of the Ce 3+ ions.…”

Review of Cholorosilicates as Phosphor Hosts

“…They published almost the same results in another paper as well. [ 106 ] Li et al. [ 107 ] confirmed these observations.…”

“…They published almost the same results in another paper as well. [106] Li et al [107] confirmed these observations. They deconvoluted the broad emission band into two Gaussian peaks centered at 508 and 560 nm.…”

Preparation and thermally stable luminescence properties of a new blue Sr5Cl0.75F0.25(PO4)3: Eu2+ phosphor for WLEDs

“…The wide range of absorption suggests that the phosphor can be effectively excited by n-UV LED chips (350-420 nm). Upon excitation at 277 nm, the PL spectrum of Sr 4.985 Cl 0.75 F 0.25 (PO 4 ) 3 : 0.015Eu 2+ exhibits broad blue emission band extending from 420 to 520 nm with the peak at 445 nm, which is attributed to the electric-dipole allowed 4f-5d transition of Eu 2+ ions [21]. At the excitation of 341 nm, the PL spectrum of the phosphor presents no significant changes except for the emission intensity.…”