Fine-grained phosphors for red-emitting mini-LEDs with high efficiency and super-luminance

Abstract

Mini-LED backlights, combining color conversion materials with blue mini-LED chips, promise traditional liquid crystal displays (LCDs) with higher luminance, better contrast, and a wider color gamut. However, as color conversion materials, quantum dots (QDs) are toxic and unstable, whereas commercially available inorganic phosphors are too big in size to combine with small mini-LED chips and also have strong size-dependence of quantum efficiency (QE) and reliability. In this work, we prepare fine-grained Sr2Si5N8:Eu2+-based red phosphors with high efficiency and stability by treating commercially available phosphors with ball milling, centrifuging, and acid washing. The particle size of phosphors can be easily controlled by milling speed, and the phosphors with a size varying from 3.5 to 0.7 μm are thus obtained. The samples remain the same QE as the original ones (∼80%) even when their particle size is reduced to 3.2–3.5 μm, because they contain fewer surface suspension bond defects. More importantly, SrBaSi5N8:Eu2+ phosphors show a size-independent thermal quenching behavior and a zero thermal degradation. We demonstrate that red-emitting mini-LEDs can be fabricated by combining the SrBaSi5N8:Eu2+ red phosphor (3.5 μm in size) with blue mini-LED chips, which show a high external quantum efficiency (EQE) of above 31% and a super-high luminance of 34.3 Mnits. It indicates that fine and high efficiency phosphors can be obtained by the proposed method in this work, and they have great potentials for use in mini-LED displays.

Layered structure-induced quenching delay toward highly efficient and thermally stable red emission in Eu3+-activated borotellurate phosphors

“…3,4 Another is a near-ultraviolet (NUV) LED chip covering blue, green, and red phosphors, which maintains good luminous efficiency and superior color uniformity. 5,6 Therefore, developing red-emitting phosphors with excellent thermal stability, high quantum yield, and good color purity (CP) is significant for improving the lighting quality of w-LEDs. 7,8 To date, a lot of highly efficient red phosphors have been developed, such as Sr 1.98Àx (Ca 0.55 Ba 0.45 ) x Si 5 N 8 :Eu 2+ and K 2 TiF 6 :Mn 4+ .…”

Synthesis of efficient submicron γ-AlON Mn2+, Mg2+ phosphors for mini-LEDs by a coprecipitation precursor method

“…10 Research has shown that ball-milled Sr 2 Si 5 N 8 :Eu 2+ also holds potential for use in mini-LED displays. 11 However, the commercial green phosphor β-Sialon:Eu 2+ with an FWHM of 55 nm fails to meet the requirements for high color gamut displays and necessitates extremely harsh preparation conditions. 12 Therefore, there is a need to develop a small-sized, high-brightness narrow-band green phosphor.…”

Luminescence Enhancement of K2LiAlF6:Mn4+ Phosphors by Zn2+-Mediated Charge Compensation for Fast-Response Backlighting Applications

“…Mini-light-emitting diodes (Mini-LEDs) are novel devices for display terminals such as TVs that can adjust the local brightness of the screen dynamically, especially in dark areas, to achieve a high contrast similar to organic LED (OLED) screens. − However, the rapid transition between light and dark regions poses a challenge for the response speed of phosphors assembled on the Mini-LEDs. − As Figure a shows, the Mini-LEDs are so small and dense that they cannot use lenses to smooth out light distribution. As a result, when the screen displays a video with a moving white circle on a black background, as in Figure b, there is uneven brightness and darkness at the border of the circle.…”