Jiacong Xu,Yanqin Miao,Jingxia Zheng,Hua Wang,Yongzhen Yang,Xuguang Liu
First, oleophilic carbon dots (CDs) with a fluorescence quantum yield (QY) of 41% were synthesized by a one-pot microwave-assisted carbonization method. Then, CD-based electroluminescent light emitting diodes (CD-LEDs) were prepared. The impact of CD aggregation on the brightness of CD-LEDs was studied. The results show that, to some extent, with the decrease of the aggregation of the CD film, the luminescence quenching of the CD-LEDs gradually decreased, and the luminance of the CD-LEDs gradually increased. Hence, in order to improve the dispersion of CDs and reduce the aggregation of CDs and the luminescence quenching of the devices, host–guest doping was adopted to effectively improve the brightness of CD-LEDs. In this work, the yellow emission of the doped devices is mainly derived from the direct carrier trapping on CDs. Moreover, white and yellow CD-LEDs were obtained from the same oleophilic CDs by tuning the structure of the devices. The white CD-LEDs exhibit a high color rendering index (CRI) of 83 with a luminance of 455.2 cd m−2. The yellow CD-LEDs show the maximum brightness of 339.5 cd m−2 and excellent color stability. The results show that the luminescence quenching of CD-LEDs was resisted and the brightness of CD-LEDs was improved by using host–guest doping.
Yellow light-emitting diodes (LEDs) with a wavelength of 570–590 nm can reduce the excitability of peripheral nerves and the sensitivity of the skin, stimulate collagen synthesis, and tighten the skin, which plays an important role in skin rejuvenation. In general, commercial LEDs are made of phosphor excited by ultraviolet chips. It is very important for the development of yellow light emitters with high luminous efficiency, good stability, and environmental protection. For the first time, a simple organic structural unit (2-methylimidazole, 2-MIM) was used to collect a mixture of two metal precursors (CsI and CuI) and successfully synthesized an all-inorganic lead-free yellow light CsCu 2 I 3 powder in water. The prepared CsCu 2 I 3 powder exhibited excellent optical properties and considerable stability. Finally, a phosphor-converted LED (pc-LED) device was fabricated via the CsCu 2 I 3 phosphor coated on a 310 nm ultraviolet chip. The pc-LED device's electroluminescence spectra may be a good fit for the blood's absorption regions. Therefore, this work provides a facile method for the synthesis of novel lead-free metal halide CsCu 2 I 3 powder in eco-friendly solvents. In addition, the stable and efficient CsCu 2 I 3 powder shows promising exciting potential applications in photoluminescence and phototherapy fields.
危险品化学品经营许可证（带存储）