Synthesis of CsPbX 3 (X = Cl/Br, Br, and Br/I)@SiO 2 /PMMA composite films as color-conversion materials for achieving t
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hool of Advanced Materials Engineering, Kookmin University, Seoul 02707, Republic of Korea Department of Organic Materials and Fiber Engineering, Soongsil University, Seoul 06978, Republic of Korea
© Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 30 June 2020 / Revised: 16 September 2020 / Accepted: 10 October 2020
ABSTRACT All-inorganic cesium lead halide based perovskite nanocrystals (PNCs) exhibit promising optoelectronic properties, but their poor stability and anion exchange reaction limit their broad commercial applications. Herein, we demonstrated the successful synthesis of blue-green-red emitting CsPbX3 (X = Cl/Br, Br, and Br/I) PNCs via hot injection method, followed by silica-coating and embedding in poly(methylmethacrylate) (PMMA) matrix. The photoluminescence (PL) spectra of SiO2/PMMA-coated PNCs can be tuned continuously by regulating precursor composition ratio, from blue (CsPb(Cl0.5/Br0.5)3; 460 nm) to red (CsPb(Br0.4/I0.6)3 via green (CsPbBr3; 519 nm). The PNCs composite films exhibit improved stability (thermal-, moisture-, and photo-stability) because of the barrier formed by SiO2/PMMA coating and also displayed exceptional photoluminescent quantum yield (PLQY of blue, green, and red-emitting SiO2/PMMA coated PNCs are 37%, 86%, and 71%, respectively) with longer lifetimes inhibiting anion exchange. Eventually, the PNCs-encapsulated SiO2/PMMA composite films were integrated into the UV LED chip as down-converting materials to construct a prototype white-peLED unit. The designed white-peLED unit demonstrated bright white light generating CIE coordinates (0.349, 0.350), a luminous efficiency (LE) of 39.2% and a color rendering index (CRI) of 84.7. The wide color gamut of 121.47% of NTSC and 98.56% of Rec. 2020 is also achieved with the built w-LED system. Therefore, the results demonstrated that CsPbX3 (X = Cl/Br, Br, and Br/I) PNCs@SiO2/PMMA composite films can be employed as efficient UV to visible color conversion materials for white-LEDs and backlighting.
KEYWORDS lead halide perovskite nanocrystals, hot-injection method, long term stability, PL quantum yield, SiO2/PMMA encapsulation, white peLED performance
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Introduction
Though the world is changing at the speed of light towards the future, the never-ending quest for alternative energy sources to solve the energy crisis remains as one of the major challenges. The rapid production of light-emitting diodes (LEDs) has now become the most energy-efficient and environment-friendly technology in the area of solid-state lighting (SSL). In particular, the availability of white LEDs with high efficiency was realized with the invention of GaN-based blue LEDs by Nakamura et.al [1-4]. White LEDs have created a significant impact on the SSL and digital display technologies over conventional lighting sources, both technically and commercially, to meet the extensive energy-saving demands. In the current scenario, enhancing energy efficiency at a rapid pace in a cost-effective and environmentally sustain
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