Yong Liu,Zhi Zhou,Lin Huang,Mikhail G. Brik,Shuaichen Si,Litian Lin,Tongtong Xuan,Hongbin Liang,Jianbei Qiu,Jing Wang
Narrow-band red-emitting fluoride phosphors for wide color gamut LED backlights have evoked considerable attention, due to their fascinating optical properties. Unfortunately, poor moisture resistance often restricts their further applications in optoelectronics. Herein we developed a Cs2SiF6:Mn4+ red phosphor using a low-temperature co-precipitation method and passivating it by using H2O2. The phosphor shows a very high external quantum efficiency (EQE) of ∼85% and exhibits excellent moisture stability retaining 74% of its emission intensity after being exposed to high temperature (85 °C) and high humidity (85%) (HTHH) for 168 h. Finally, the high brightness white LED devices combined with the passivated Cs2SiF6:Mn4+ exhibit high luminous efficacy of 133 lm W−1 and wide color gamut (∼84.7% NTSC). The results demonstrate that the passivated Cs2SiF6:Mn4+ with high EQE and excellent moisture-resistance is promising as a narrow-band red emitting phosphor for wide color gamut LED backlights.
Investigating narrow-band green emitting phosphors with high efficiency and good thermal stability is the main goal of the present light-emitting diode (LED) display research. Here, Ba1−xCaxScO2F:0.001Bi3+,0.001K+ (x = 0–0.12) perovskite phosphors, emitting narrow green light excited by a 415 nm chip, were developed using the cation substitution design strategy. The effects of Ca2+ substitution for Ba2+ in the Ba1−xCaxScO2F:0.001Bi3+,0.001K+ crystal structures and photoluminescence properties were investigated. All the phosphors show the cubic perovskite-type structure in the space group Pm3m. The evolution of the cell parameters and the Ba/Ca/K/Bi–O bond lengths were evaluated. The phosphors with the internal quantum efficiency of 77.4% exhibit bright green emission peaking at 510 nm under 415 nm chip excitation. The improvement of luminescence efficiency and thermal stability was discussed in detail in relation to the local structure variation. The cation substitution design strategy mentioned here can become an important approach to realize the spectral modulation through controlling the micro-environment in the lattice for excellent LED backlight displays.
Dan Li,Yixuan Liu,Shuangshuang Shi,Yanjun Li,Chong Geng,Shu Xu
Lead halide perovskite nanocrystals (PNCs) are emerging as promising light-conversion materials for light-emitting diode (LED) display applications. However, the practical application of PNCs is hindered by their labile surface and dynamic ionic ligand binding. Here, we report a post-synthetic surface passivation strategy to stabilize the CsPbBr3 PNCs by zinc methacrylate (ZnMA) and trioctylphosphine oxide (TOPO) co-passivation. Surface analyses reveal that the ZnMA stabilizes the PNCs by replacing the surface ammonium ligands, and TOPO further coordinates to the ZnMA to provide a high photoluminescence quantum yield (PLQY) of the PNCs. Moreover, the ZnMA capping on the PNC surface could participate in the polymerization of MMA to form a crosslinked polymer shell around the PNCs. The resultant PNCs–PMMA film presents a PLQY of 74% and maintains a constant PL intensity under continuous UV irradiation in air, while the PNCs–PMMA film made of classical PNCs quickly degrades. The prepared PNCs–PMMA film was tested as the light down-conversion layer in LED backlighting and presented photostability comparable to classical CdSe/ZnS NCs–PMMA under continuous illumination. This surface passivation strategy avoids the use of ionic ligands for the surface passivation of PNCs in polymer matrices, and we expect related surface chemistry to promote the performance enhancement of diverse PNCs–polymer composites for LEDs and other optoelectronic applications.
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