制备不含稀土元素、价格低廉且对环境友好的单相量子点发光材料, 对于实现白光量子点二极管(WQLEDs)的大规模商业化应用至关重要. 用一步水热法合成了硫化锌量子点(ZnS-QDs), 其热分解温度高达680 ℃, 荧光量子产率为16.3%. 通过紫外吸收光谱和理论计算探讨了ZnS-QDs的锌空位发光机理, 并制备出发标准白光的WQLEDs, 工作电流在300 mA时的国际照明委员会(CIE)坐标为(0.3725, 0.4006), 显色指数(CRI)为76.6, 相关色温(CCT)为4500 K, 三色比(R, G, B)为R=14.6%, G=83.5%, B=1.8%, 红绿蓝三种颜色中绿光占比最多, 蓝光含量最少, 有利于眼睛的保护. 该研究实现了使用无稀土掺杂的单相量子点制备WQLEDs的目标.

Preparation of undoped rare earth element, inexpensive and environmentally friendly single-phase quantum dots luminescent materials is crucial for realizing large-scale commercial application of white-light quantum dots diodes (WQLEDs). In this work, zinc sulfide quantum dots (ZnS-QDs) were prepared by a one-step hydrothermal method. The experimental method was to add zinc acetate into the mixed solution of water and ethanol, adjust the pH to 5~6, and then add thiourea. All raw materials were evenly mixed and put into a high-temperature hydrothermal reactor, and then ZnS-QDs was synthesized under the high-temperature condition of 240 ℃. By changing the ratio of water and ethanol in the solution and adjusting the pH, ZnS-QDs was obtained. The fluorescence emission peak of ZnS-QDs was about 535~566 nm. The thermogravimetric analysis of the obtained ZnS-QDs showed that the thermal decomposition temperature was up to 680 ℃. The measured fluorescence quantum yield was 16.3%. The luminescence mechanism of zinc vacancy in ZnS-QDs and the influence of changing synthesis conditions on the band gap width were discussed by UV absorption spectrum and theoretical calculation. After the mixture of ZnS-QDs phosphors and organic silica gel was dropped on the ultraviolet LED chip with the excitation light source of 365 nm, the input voltage was 3.4 V and the current was 100~500 mA, the light was lit. Standard white quantum dot LEDs were obtained. The international commission on illumination (CIE) coordinates of WQLEDs at 300 mA are (0.3725, 0.4006), the color rendering index (CRI) is 76.6 and the correlation color temperature (CCT) was 4500 K. The tricolor ratio (R, G, B) was R=14.6%, G=83.5%, B=1.8%. It could be seen that green was the majority of the three colors, and the blue content was relatively small, which was conducive to the protection of eyes. This study provides a promising method for realizing WQLEDs using single-phase quantum dots.