离子液体辅助微波法水相合成Cu-In-Zn-S/ZnS量子点及其在白光LED中的应用

Ionic Liquid Assisted Microwave Synthesis of Cu-In-Zn-S/ZnS Quantum Dots and Their Application in White LED

Cu-In-Zn-S(CIZS)量子点具有毒性低、发射谱覆盖范围广、Stokes位移大等特点,在照明领域具有广阔的应用前景。通过离子液体辅助微波法水相合成CIZS量子点,系统研究了反应时间、配体添加量和前驱体溶液pH对样品的物相组成、显微形貌以及荧光性能的影响。结果表明,与未添加离子液体制备的样品相比,离子液体的引入提高了反应速率,可有效地将反应时间由180min缩短至30min;随着反应时间的延长,量子点的粒径增大,其发射峰位由609.2nm红移至634.6nm。随着nGSH(谷胱甘肽)/n(CuInZn)的增大,量子点的粒径逐渐增大,导致其发射峰位由622.6 nm红移至631.6 nm,同时量子点的发光强度逐渐增强;当该比值为15时,量子点的荧光强度最高。此外,随着pH的增大,去质子化的–SH和–NH2与量子点的作用逐渐增强,有效地钝化了量子点的表面态,使其荧光强度逐渐上升,当pH为8.5时,样品的荧光性能最佳,同时量子点的平均水合粒径由99nm增大至241nm;量子点溶液的Zeta电位为–27.7~–41.1mV,说明量子点溶液具有优异的稳定性。通过ZnS表面修饰可有效提高量子点的荧光强度。将CIZS/ZnS量子点与蓝光芯片结合,获得了显色指数为85.6、发光效率为34.8 lm/W的白光LED器件,为水相制备的多元量子点在白光LED中的应用提供了参考。

Cu-In-Zn-S(CIZS) quantum dots(QDs) are considered as promising fluorescent materials owing to their low toxicity, wide emission range and large Stokes shifts, which have a wide prospect in lighting field. CIZS QDs were prepared via ionic liquid assisted microwave method in aqueous solution. The effects of reaction time, addition amount of ligand and pH of precursor solution on phase composition, microscopic morphology and photoluminescence(PL) property were investigated. Results showed that the reaction rate could be accelerated with the assistance of ionic liquid, i.e. the reaction time reducing from 180 min to 30 min. The size of QDs gradually increased with the increase of reaction time, resulting in red shift of emission peak from 609.2 to 634.6 nm. Moreover, the particle size of CIZS QDs increased with the increase of nGSH/n(CuInZn) ratios, resulting in the red shift of emission peak from 622.6 nm to 631.6 nm. Meanwhile, the PL intensity of QDs increased and reached the maximum at nGSH/n(CuInZn)=15. Furthermore, the surface defect state was effectively passivated with the increase of pH of precursor solution due to enhanced bonding force between deprotonized groups(–SH, –NH2) and QDs, resulting in enhancement of PL intensity. And the optimal pH was 8.5. The average hydrodynamic size of CIZS QDs increased from 99 nm to 241 nm with the increase of pH, and the relative Zeta potential ranged from –27.7 mV to –41.1 mV, indicating the excellent stability of CIZS QDs solution. Emission intensity of QDs could be enhanced significantly after coating with ZnS shells. White LED device was fabricated by combining CIZS QDs and a blue chip, the color rendering index and luminous efficiency of device were 85.6 and 34.8 lm/W, respectively, which provided a reference for the application of water soluble multiple QDs in white LEDs.