基于单一基碳点白光荧光粉的LED

发布时间：2018-08-26 11:14

【摘要】：发光二极管（LED）具有能耗低、光效高以及寿命长等优点，近年来受到科学界和产业界的广泛关注。实际应用中，以单一基质白光荧光粉的研究最为关键。白光LED用荧光粉分为稀土基荧光粉、胶体量子点荧光粉以及碳点（Carbon dots，CDs）荧光粉三大类。其中，CDs由于具有荧光量子产率高、稳定性高及毒性低等优点，成为近年来发光材料研究的热点。 为了提高白光LED用CDs荧光粉的荧光量子产率和蓝、绿、红光总比重，本论文以一水合柠檬酸为碳源，分别以乙二胺、硫脲和L-半胱氨酸为添加剂，在不同温度下水热反应6h，制得氮掺杂碳点（Nitrogen-doped CDs,N-CDs）与氮硫掺杂碳点（Nitrogen and sulphur-doped CDs, NS-CDs），并对其进行结构和光学性质分析。优选荧光量子产率最高且蓝、绿、红光总比重较高的产物N-CDs4和NS-CDs9，并以其为荧光粉制作了白光LED，对白光LED的色坐标和相关色温（Correlated color temperature, CCT）进行了表征。 通过研究，得到以下结论： (1) N-CDs的制备与性质。随着乙二胺添加量的增加，N-CDs的荧光量子产率先增高、后降低。在160-200℃内，其荧光量子产率基本不随反应温度的变化而变化。乙二胺添加量和反应温度基本不影响N-CDs的光谱组成。当一水合柠檬酸与乙二胺摩尔比为1:4，反应温度为200℃时，得到最优N-CDs4，其荧光量子产率为67.06%；在光谱中，，红、绿、蓝光总比重为53.01%，均高于目前文献所报道的最高值。具有两个荧光中心，寿命为17.0ns的荧光中心向寿命为11.1ns的荧光中心发生了能量转移。C-N基团的引入能够提高N-CDs的荧光量子产率。 (2) NS-CDs的制备与性质。随着硫脲添加量的增加，含C=S官能团NS-CDs的荧光量子产率先增高、后降低；在160-200℃内，该NS-CDs的荧光量子产率随反应温度的升高而增加；蓝、绿、红光总比重随硫脲添加量和反应温度的增加而降低。当一水合柠檬酸与硫脲摩尔比为1:1，反应温度为200℃时，得到最优NS-CDs3。其荧光量子产率为9.80%；在光谱中，红、绿、蓝光总比重为47.82%；平均荧光寿命为8.88ns；其荧光衰减曲线符合三指数函数，意味着NS-CDs3有三个荧光中心。 而含有C-S官能团的NS-CDs9的荧光量子产率高达65.37%，红、绿、蓝光总比重高达61.93%。较C-S官能团，C=S官能团不利于CDs荧光量子产率的提高。S元素的引入能够有效提高NS-CDs的蓝、绿、红光总比重。 (3)白光LED的制备与光学性能。采用具有最高荧光量子产率和较高蓝、绿、红光总比重的N-CDs4和NS-CDs9作为荧光粉制备了白光LED。N-CDs4基白光LED色坐标为（0.38，0.42），CCT为4290K。NS-CDs9基白光LED色坐标为（0.32,0.36），CCT为5822K。光学密封胶和聚乙烯醇水凝胶使CDs发射光谱产生明显红移，全部覆盖可见光区。实现LED直接发射白光。
[Abstract]:Light emitting diode (LED) has attracted much attention in recent years because of its advantages of low energy consumption, high light efficiency and long lifetime. In practical application, the study of single substrate white phosphor is the most important. White LED phosphors are divided into three categories: rare earth based phosphors colloidal quantum dots phosphors and carbon dots (Carbon dots,CDs) phosphors. Due to their advantages of high fluorescence quantum yield, high stability and low toxicity, CDs have become a hot spot in the research of luminescent materials in recent years. In order to improve the fluorescence quantum yield and the specific gravity of blue, green and red light of CDs phosphors for white LED, in this paper, citric acid monohydrate was used as carbon source, ethylenediamine, thiourea and L-cysteine were used as additives, respectively. Nitrogen doped carbon point (Nitrogen-doped CDs,N-CDs) and nitrogen sulfur doped carbon point (Nitrogen and sulphur-doped CDs, NS-CDs) were prepared by hydrothermal reaction at different temperatures for 6 h, and their structures and optical properties were analyzed. N-CDs4 and NS-CDs9, which have the highest fluorescence quantum yield and blue, green and high specific gravity of red light, were selected, and the white LED, was used as phosphors to characterize the color coordinates and related color temperature (Correlated color temperature, CCT) of white LED. The main conclusions are as follows: (1) preparation and properties of N-CDs. With the addition of ethylenediamine, the fluorescence quantum production of N-CDs firstly increased and then decreased. In the temperature range of 160 鈩

本文编号：2204696