Y3Al5O12:Ce3+ (YAG:Ce3+) nanocrystals were synthesized in 1,4-butylene glycol (BG) with and without poly(ethylene glycol) (PEG) by the glycothermal method. The internal quantum efficiency of the photoluminescence (PL) corresponding to the 5d --> 4f transition of Ce3+ in the YAG:Ce3+ nanocrystal increased from 21.3 to 37.9% by addition of PEG, while no appreciable change in the primary particle size, the crystallite size, and the lattice distortion was recognized by transmission electron microscopy and X-ray diffractometry. The thermogravimetry-differential thermal analysis, Fourier transform infrared absorption spectroscopy and 1H --> 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) confirmed the preferential coordination of PEG to the YAG:Ce3+ nanocrystal. 27Al single-pulse excitation MAS NMR reveals that the ratio of the 4-fold coordination site to the 6-fold coordination site increased from 0.53 to 0.72 by addition of PEG. We conclude that the surface modification of the YAG:Ce3+ nanocrystal by PEG induces the surface passivation, the prevention of the oxidation of Ce3+ to Ce4+, the promotion of the incorporation of Ce3+ into YAG and the local structural rearrangement, resulting in the PL enhancement.

The authors produced the transparent color conversion thick film which is composed of a high concentration of YAG:Ce3+ nanoparticles prepared by glycothermal method, and characterized its optical properties. The transmittance of the 200μm thick film with the nanoparticle content 70.7wt% was 82% at 525nm corresponding to the emission peak of YAG:Ce3+. The intensity of photoluminescence due to the 5d→4f transition of Ce3+ in YAG:Ce3+ nanoparticles was doubled by placing a reflection mirror at the back of the transparent film. Judging from this result, the transparent film of YAG:Ce3+ nanoparticles has markedly low scattering loss.

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The concept of van der Waals solid solutions has been demonstrated to yield photon upconversion (UC) organic crystals with extraordinary performance, opening a domain of versatile dispersion-force-based systems in the quest for superior UC solids.

The authors applied two technologies to improve the efficiency of fluorescent blue organic light-emitting diodes (OLEDs). First, an efficiency-enhancement layer (EEL) was introduced to boost triplet–triplet fusion (TTF). Second, new blue dopants with a higher orientation factor in the emitting layer were developed. Consequently, the external quantum efficiency (EQE) was increased up to 11.5% with Commission Internationale de l’Eclairage (CIE) 1931 color coordinates of (0.138, 0.092). The reported results may lead to EQEs that exceed 14% with fluorescent blue emitters.