Red-emitting carbon dots phosphors: a promising red color convertor toward warm white light emitting diodes
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Red-emitting carbon dots phosphors: a promising red color convertor toward warm white light emitting diodes Rongrong Yuan1 · Jianming Liu1 · Weidong Xiang1 · Xiaojuan Liang1 Received: 28 March 2018 / Accepted: 12 April 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018
Abstract Various luminescent carbon materials are artificially synthesized and as admirable fluorescent materials because of the increased research of carbon nanodots (CDs). Herein, a novel solvent-dependent red CDs (rCDs) is introduced through solvothermal method. The as-prepared rCDs remain benzene structure and possess abundant surface function groups that endow them well solubility in various solvents. Furthermore, multicolor luminescence are observed when rCDs are dissolved in different solvents, and the emission wavelength of these materials can be well-tuned from 475 to 624 nm, which presents intensity solvent-dependent properties. Red luminescence carbon phosphors are successfully synthesized by mix rCDs with silica powder. Finally, warm white light emitting diodes (WLEDs) are constructed using rCDs powder with Ce3+: YAG single crystal and blue GaN chips. The results demonstrate that the rCDs can act as red component to modify the correlated color temperature (CCT) and the color rendering index (CRI) of WLEDs .
1 Introduction It is well known to us all is that white light emitting diodes (WLEDs) were born for it’s advantages of low power consumption, long working time as well as high energy efficiency [1]. Currently, the most popular WLEDs are constructed based on the combination of blue InGaN blue chip and traditional green/yellow phosphors, such as Y3Al5O12:Ce3+(Ce:YAG) [2], Sr3SiO5:Ce3+ [3]. The most effectively phosphors layer is Ce:YAG phosphors layer, the highest luminous efficacy (LE) up to 134.33 lm W −1 [4]. However, red colour component is still lack result in the color rendering index (CRI) is only 68.5 and this value decided the prepared WLEDs based on Ce:YAG,are inadequacy applied in place where color is need to be judged correctly (standard CRI is in range of 80–100). Therefore, many different red phosphors, including nitrides (e.g., E u2+: Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10854-018-9103-3) contains supplementary material, which is available to authorized users. * Weidong Xiang [email protected] * Xiaojuan Liang [email protected] 1
Wenzhou University, Wenzhou, China
CaAlSiN3) [5], sulfides (e.g., E u2+: CaS) [6] or fluoride (e.g., Mn4+:K2MF6, M=Ge or Si) [7] have been developed to improve the performance of the warm WLEDs. However, the synthesis of market red fluorescent powders always need harsh conditions, such as high reaction temperature and reductive atmosphere, which are industrially unfavourable. Currently, carbon dots (CDs) materials are emerge as a promising optical materials owe to their merits of broad luminescence peak, low photobleaching, benign chemical stability, superior optical properties, well solubil
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