Zhidong

The last decade has witnessed the remarkable research progress of lanthanide-doped upconversion nanocrystals (UCNCs) at the forefront of promising applications. However, the future development and application of UCNCs are constrained greatly by their underlying shortcomings such as significant nonradiative processes, low quantum efficiency, and single emission colors. Here a hybrid plasmonic upconversion nanostructure consisting of a GNR@SiO₂ coupled with NaGdF₄:Yb³⁺,Nd³⁺@NaGdF₄:Yb³⁺,Er³⁺@NaGdF₄ core–shell–shell UCNCs is rationally designed and fabricated, which exhibits strongly enhanced UC fluorescence (up to 20 folds) and flexibly tunable UC colors. The experimental findings show that controlling the SiO₂ spacer thickness enables readily manipulating the intensity ratio of the Er³⁺ red, green, and blue emissions, thereby allowing us to achieve the emission color tuning from pale yellow to green upon excitation at 808 nm. Electrodynamic simulations reveal that the tunable UC colors are due to the interplay of plasmon-mediated simultaneous excitation and emission enhancements in the Er³⁺ green emission yet only excitation enhancement in the blue and red emissions. The results not only provide an upfront experimental design for constructing hybrid plasmonic UC nanostructures with high efficiency and color tunability, but also deepen the understanding of the interaction mechanism between the Er³⁺ emissions and plasmon resonances in such complex hybrid nanostructure.

The plasmon-mediated selective excitation and emission enhancement on the blue, green, and red emissions of Er³⁺ in a rationally designed hybrid plasmonic upconversion (UC) nanostructure enables achieving enhanced UC luminescence and tunable UC color.

Negative polaron stabilizing host materials for blue phosphorescence organic light-emitting diodes are synthesized by modifying carbazolylcarbazole with dibenzothiophene or 9-phenylcarbazole. The host materials show high triplet energy above 2.95 eV and work as hole transport type hosts. Operational lifetime analysis of the blue devices with the two hosts demonstrates that the dibenzothiophene modified carbazolylcarbazole host functions better than the 9-phenylcarbazole modified carbazolylcarbazole host. Improved negative polaron stability from bond dissociation energy calculation and single carrier aging test results is the main factor for the lifetime extension in the dibenzothiophene modified carbazolylcarbazole host based blue phosphorescent organic light-emitting diodes.

The host materials for blue phosphorescent organic light-emitting diodes are designed to reinforce negative polaron stability. The synthesized blue host material, 9-(dibenzo[b,d]thiophen-2-yl)-9H-3,9′-bicarbazole exhibits a very high triplet energy of 2.97 eV and shows improved device operational lifetime due to improved intrinsic bond stability against negative polarons.