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A series of innovative thermosetting polymer nanocomposites comprising of polysiloxane-imide-containing benzoxazine (PSiBZ) as the matrix and double-decker silsesquioxane (DDSQ) epoxy or polyhedral oligomeric silsesquioxane (POSS) epoxy were prepared for improving thermosetting performance. Thermomechanical and dynamic mechanical characterizations indicated that both DDSQ and POSS could effectively lower the coefficient of thermal expansion by up to approximately 34% and considerably increase the storage modulus (up to 183%). Therefore, DDSQ and POSS are promising materials for low-stress encapsulation for electronic packaging applications.

To realize high-efficiency AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs), enhancing their light-extraction efficiency (LEE) is crucial. This paper proposes an aluminum-based sidewall reflector structure that could replace the conventional ceramic-based packaging method. We design optimization simulations and experimental results demonstrated the light power output could be enhanced 18.38% of DUV-LEDs packaged with the aluminum-based sidewall.

We demonstrate excellent color quality of liquid-type white light-emitting diodes (WLEDs) using a combination of green light-emitting CsPbBr3 and red light-emitting CdSe/ZnS quantum dots (QDs). Previously, we reported red (CsPbBr1.2I1.8) and green (CsPbBr3) perovskite QDs (PQDs)-based WLEDs with high color gamut, which manifested fast anion exchange and stability issues. Herein, the replacement of red PQDs with CdSe/ZnS QDs has resolved the aforementioned problems effectively and improved both stability and efficiency. Further, the proposed liquid-type device possesses outstanding color gamut performance (132% of National Television System Committee and 99% of Rec. 2020). It also shows a high efficiency of 66 lm/W and an excellent long-term operation stability for over 1000 h.

This study presents a novel method for estimating the phosphor conversion efficiency of white light-emitting diodes (WLEDs) with different ratios of phosphors. Numerous attempts have been made for predicting the phosphor conversion efficiency of WLEDs using Monte Carlo ray tracing and the Mie scattering theory. However, because efficiency depends on the phosphor concentration, obtaining a tight match between this model and the experimental results remains a major challenge. An accurate prediction depends on various parameters, including particle size, morphology, and packaging process criteria. Therefore, we developed an efficient model that can successfully correlate the total absorption ratio to the phosphor concentration using a simple equation for estimating the spectra and lumen output. The novel and efficient method proposed here can accelerate WLED development by reducing costs and saving fabrication time.

This study investigated a new category of transparent encapsulant materials for light-emitting diodes (LEDs). It comprised a phenyl group that contained siloxane-modified epoxy (SEP-Ph) hybridized with a cyclic tetrafunctional siloxane-modified epoxy (SEP-D4) with methylhexahydrophthalic anhydride (MHHPA) as a curing agent. The SEP-Ph/SEP-D4 = 0.5/0.5 (sample 3) and SEP-D4 (sample 4) could provide notably high optical transmittance (over 90% in the visible region), high-temperature discoloration resistance, low stress, and more crucially, noteworthy sulfurization resistance. The lumen flux retention of the SEP encapsulated surface mounted device LEDs remained between approximately 97% and 99% after a sulfurization test for 240 h. The obtained comprehensive optical, mechanical, and sulfurization resistance proved the validity and uniqueness of the present design concept with complementary physical and chemical characteristics.Polymers 2020, 12, 21 2 of 11 of anhydride hardener and accelerator [14,15]. Huang et al. developed a series of cyclic silicone epoxies with various numbers of epoxy groups. By curing with aluminum acetylacetonate (Al(acac) 3 ) and diphenylsilanediol (Ph 2 Si(OH) 2 ), enhanced ultraviolet stability was achieved compared with an anhydride-cured cycloaliphatic epoxy [16]. Hue et al. prepared a transparent composition using the diglycidyl ether of bisphenol A and a phenylmethylsiloxane-modified epoxy (PMSE) hybrid resin. Curing with methylhexahydrophthalic anhydride (MHHPA) revealed that the addition of an appropriate amount of PMSE could effectively improve high-temperature thermal stability, dynamic mechanical stability, and performance of LEDs [18].Currently, surface mounted device LEDs (SMD LEDs) are advancing and their packages are becoming smaller and thinner. This allows harmful contaminants in the atmosphere such as hydrogen sulfide (H 2 S) to easily permeate an LED's package through its transparent encapsulation material.In this case, the bottom silver electrodes would darken because of the formation of silver sulfide, which would be accompanied by a significant decrease in the LED's light output. Although transparent epoxy-based encapsulants exhibit suitable gas barrier properties, the high thermal stress of epoxy resins that is generated during the soldering or temperature-cycling process would cause catastrophic damage. By contrast, silicone materials possess relatively low thermal stress compared with conventional epoxy resins, but their higher gas permeation properties would pose a problem for thin SMD LED packages, especially in outdoor applications.Many research studies have been conducted to enhance the gas barrier properties of transparent polymers, one of which added nanoscale lamellar fillers with a large aspect ratio, such as clay or graphene, into the polymer matrix [19,20]. The addition of clay can alter and extend the gas molecule diffusion pathway; furthermore, the incorporation of graphene can effectively prevent gas molecules from permeating into the polymer matrix; ho...