Abstract
Quantum dots (QDs) have been widely applied in luminescent sources due to their strong optical characteristics. However, a moisture environment causes their quenching, leading to an inferior optical performance in commercial applications. In this study, based on the high moisture resistance of epoxy resin, a novel epoxy/QDs composite particle structure was proposed to solve this issue. Flexible luminescent films could be obtained by packaging composite particles in silicone resin, combining the hydrophobicity of epoxy resin and the flexibility of PDMS simultaneously. The photoluminescence and light extraction were improved due to the scattering properties of the structure of composite particles, which was caused by the refractive index mismatch between the epoxy and silicone resin. Compared to the QD/silicone film under similar lighting conditions, the proposed flexible film demonstrated increased light efficiency as well as high moisture stability. The results revealed that a light-emitting diode (LED) device using the composite particle flexible (CPF) structure obtained a 34.2% performance enhancement in luminous efficiency as well as a 32% improvement in color conversion efficiency compared to those of devices with QD/silicone film (QSF) structure. Furthermore, the CPF structure exhibited strong thermal and moisture stability against extreme ambient conditions of 85 °C and 85% relative humidity simultaneously. The normalized luminous flux degradation of devices embedded in CPF and QSF structures after aging for 118 h were ~20.2% and ~43.8%, respectively. The satisfactory performance of the CPF structure in terms of optical and moisture stability shows its great potential value in flexible commercial QD-based LED displays and lighting applications.
Highlights
Introduction iationsQuantum dots (QDs) have been attracting great attention and have gradually become one of the most promising color-conversion materials in white light-emitting diodes (LEDs), because of their high quantum yield, high color rendering quality, and narrow emission angle [1,2,3,4,5,6]
It can be observed that the composite particles with spherical morphology exhibit a good dispersion and present a uniform diameter distribution
The composite particles exhibit a concentrated distribution with an average diameter of about 40 μm
Summary
CdSe/ZnS core-shell QDs with an emission peak of 570 nm were bought from Beida Jubang Co. 120 mg of QDs was dissolved in chloroform, followed by the addition of 4 g of epoxy resin (IK0010, IK INABATA & Co., Ltd., Tokyo, Japan) into the mixture. In order to completely volatile the chloroform, the mixture was subjected to centrifugal stirring with 400 rpm revolution rate and 300 rpm rotation rate for 2 h using a mixer (FY-821, Shenzhen Fuyuanxiang Electronic Equipment Co., Ltd., Shenzhen, China). The curing films were cut into small pieces and ground at 450 rpm for 5 h by a ball grinder.
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