Na Replaces Rb towards High‐Performance Narrow‐Band Green Phosphors for Backlight Display Applications

Abstract

The improvement of high‐performance narrow‐band green phosphors in backlight display applications is still a major challenge. Based on the UCr4C4 type of oxide phosphor, the high‐performance narrow‐band green phosphors Rb3M(Li3SiO4)4:Eu2+ (M = Rb or Na) are studied in different luminous positions. Benefiting from the replacement of Rb by Na, the change of the local environment in the crystal structure of Rb3Na(Li3SiO4)4:Eu2+ (R3NLSO:Eu2+) leads to the decrease of Stokes shift, which improves the quantum efficiency. Moreover, change in the local environment enhances the structural rigidity, which makes the thermal and chemical stability better. The R3NLSO:8%Eu2+ phosphor presents a narrow‐band green emission centered at 527 nm, excellent thermal stability (102% @150 °C of the integrated emission intensity at room temperature), and high internal/external quantum efficiency (85.3%/40.4%). The white light‐emitting diode (wLED) using R3NLSO:8%Eu2+ phosphor presents a superior luminous efficiency of 128.3 lm W‐1 and a wide color gamut. All the results indicate that R3NLSO:8%Eu2+ green phosphor has great application prospects in the field of liquid crystal display. This work also provides important guiding significance for the optimization of alkali metal element type of phosphors.

Accurately Controlling the Occupation of Eu2+ in Cs(K, Na)3(Li3SiO4)4 to Achieve Narrow-Band Green Emission for Wide Color Gamut Displays

“…As a result, when the temperature reaches the backlight working temperature (423 K), the integrated emission intensity of CK 1.9 NLSO: 10%Eu 2+ remains 96.3% of that at RT, and the intensity of the peak at 531 nm is still 85.5% of that at RT. Generally, the spectrum broadening effect occurs at high temperature, but the fwhm of CK 1.9 NLSO: 10%Eu 2+ at 423 K is also lower than that of the commercial green phosphor β-SiAlON: Eu 2+ at RT (54 nm). ,, In addition, the narrow-band green phosphor CK 1.9 NLSO: 10%Eu 2+ also has excellent performance at low temperature. The integrated emission intensity and the intensity of the peak (531 nm) at 300 K still are maintained as 94.9% and 84.8% of those at 80K, respectively.…”

“…Furthermore, one Eu 2+ replaces two monovalent cations and forms a vacancy to balance the charge. 7,14 To verify the match of the CKN 2 LSO and CK 2 NLSO matrices to the standard card (ICSD-74864), the Rietveld refinement XRD pattern is validated (Figure 2a,b). The refined parameter results are within the acceptable range, as shown in Table 1.…”

“…Since Eu 2+ and Na + have closer radius, Eu 2+ occupies Na + sites more preferentially. Furthermore, one Eu 2+ replaces two monovalent cations and forms a vacancy to balance the charge. , …”

“…On the basis of the Kubelka–Munk function, , the band gap of CK 2 NLSO can be estimated to be 5.74 eV, as shown in Figure S1f. Since the broad optical band gap can reduce the probability of excited electrons being thermal ionization, CK 2 NLSO is an appropriate compound for luminescent materials …”

Role of the Rigid Host Structure in Narrow-Band Green Emission of Eu2+ in Rb2Na2(Li3SiO4)4: Insights into Electron–Phonon Coupling

“…For instance, broad-band emitting phosphors are suitable for achieving high color rendition in white light-emitting diodes, and narrow-band emission (FWHM < 50 nm) is desirable for backlighting phosphors in display devices to accomplish high color rendition and wide gamut. , Recently, Eu 2+ -activated narrow-band UCr 4 C 4 -type phosphors have received significant attention, starting with the pioneering red-emitting nitride phosphor SrLiAl 3 N 4 :Eu 2+ . Among these, the alkali-lithosilicate phosphors with the general formula M 4 (Li 3 SiO 4 ) 4 (M is an alkali metal ion) are presented to be a versatile system to achieve narrow-band emissions of different colors through combination of the four M cations. − As an example, Rb 2 Na 2 [Li 3 SiO 4 ] 4 :Eu 2+ displays thermally stable narrow-band emission at room temperature under blue-light excitation, peaking at 523 nm with FWHM = 41 nm (1501 cm –1 ), which is attractive because human eyes are most sensitive to green light …”