Li Feng, Nie Chao, You Lai, Jin Xiao, Zhang Qin, Qin Yuancheng, Zhao Feng, Song Yinglin, Chen Zhongping, Li Qinghua
Jiangxi Engineering Laboratory for Optoelectronics Testing Technology, Nanchang Hangkong University, Nanchang, 330063, People's Republic of China.
Nanotechnology. 2018 May 18;29(20):205701. doi: 10.1088/1361-6528/aab18e. Epub 2018 Feb 22.
White light emitting diodes (WLEDs) based on quantum dots (QDs) are emerging as robust candidates for white light sources, however they are suffering from the problem of energy loss resulting from the re-absorption and self-absorption among the employed QDs of different peak wavelengths. It still remains a challenging task to construct WLEDs based on single-phase QD emitters. Here, CdS QDs with short synthesis times are introduced to the fabrication of WLEDs. With a short synthesis time, on one hand, CdS QDs with a small diameter with blue emission can be obtained. On the other hand, surface reconstruction barely has time to occur, and the surface is likely defect-ridden, which enables the existence of a broad emission covering the range of green, yellow and red regions. This is essential for the white light emission of CdS QDs, and is very important for WLED applications. The temporal evolution of the PL spectra for CdS QDs was obtained to investigate the influence of growth time on the luminescent properties. The CdS QDs with a growth time of 0.5 min exhibited a colour rendering index (CRI) of 79.5 and a correlated colour temperature (CCT) of 6238 K. With increasing reaction time, the colour coordinates of the CdS QDs will move away from the white light region in the CIE 1931 chromaticity diagram. By integrating the as prepared white light emission CdS QDs with a violet GaN chip, WLEDs were fabricated. The fabricated WLEDs exhibited a CRI of 87.9 and a CCT of 4619 K, which satisfy the demand of general illumination. The luminous flux and the luminous efficiency of the fabricated WLEDs, being less advanced than current commercial white light sources, can be further improved, meaning there is a need for much more in-depth studies on white light emission CdS QDs.
基于量子点（QD）的白光发光二极管（WLED）正成为白光光源的有力候选者，然而，它们存在因不同峰值波长的所用量子点之间的再吸收和自吸收而导致能量损失的问题。构建基于单相量子点发射体的WLED仍然是一项具有挑战性的任务。在此，将合成时间短的硫化镉量子点引入到WLED的制造中。由于合成时间短，一方面，可以获得具有蓝光发射的小直径硫化镉量子点。另一方面，表面重构几乎没有时间发生，并且表面可能充满缺陷，这使得能够存在覆盖绿色、黄色和红色区域范围的宽发射。这对于硫化镉量子点的白光发射至关重要，并且对于WLED应用非常重要。获得了硫化镉量子点的光致发光（PL）光谱的时间演化，以研究生长时间对发光性能的影响。生长时间为0.5分钟的硫化镉量子点表现出显色指数（CRI）为79.5，相关色温（CCT）为6238K。随着反应时间的增加，硫化镉量子点的色坐标将在CIE 1931色度图中从白光区域移开。通过将所制备的发白光的硫化镉量子点与紫色氮化镓芯片集成，制造出了WLED。所制造的WLED表现出CRI为87.9，CCT为4619K，满足一般照明的要求。所制造的WLED的光通量和发光效率比当前的商用白光光源要低，仍可进一步提高，这意味着需要对发白光的硫化镉量子点进行更深入的研究。
