Young Hyun Song

High-efficiency exfoliation of large-area mono-layer graphene oxide with controlled dimension

In this work, we introduce a novel and facile method of exfoliating large-area, single-layer graphene oxide using a shearing stress. The shearing stress reactor consists of two concentric cylinders, where the inner cylinder rotates at controlled speed while the outer cylinder is kept stationary. We found that the formation of Taylor vortex flow with shearing stress can effectively exfoliate the graphite oxide, resulting in large-area single- or few-layer graphene oxide (GO) platelets with high yields (>90%) within 60 min of reaction time. Moreover, the lateral size of exfoliated GO sheets was readily tunable by simply controlling the rotational speed of the reactor and reaction time. Our approach for high-efficiency exfoliation of GO with controlled dimension may find its utility in numerous industrial applications including energy storage, conducting composite, electronic device, and supporting frameworks of catalyst.

A highly efficient and stable green-emitting mesoporous silica (MP)–(Cs0.4Rb0.6)PbBr3 perovskite composite for application in optoelectronic devices

We have, for the first time, reported a highly efficient MP–(Cs0.4Rb0.6)PbBr3 luminescent material for application in optoelectronic devices. MP–(Cs0.4Rb0.6)PbBr3 with red-emitting Sr2Si5N8:Eu2+ phosphor is applied to an InGaN blue chip and compared with green-emitting (Cs0.4Rb0.6)PbBr3 perovskite nanocrystals (NCs). MP–(Cs0.4Rb0.6)PbBr3 achieves a conversion efficiency of 80.9 lm W−1 under a forward-bias current of 150 mA. We propose MP–(Cs0.4Rb0.6)PbBr3 as a promising green-emitting material that can replace the conventional inorganic phosphor.

Innovatively Continuous Mass Production Couette-taylor Flow: Pure Inorganic Green-Emitting Cs 4 PbBr 6 Perovskite Microcrystal for display technology

We report for the first time the mass production of Cs4PbBr6 perovskite microcrystal with a Couette-Taylor flow reactor in order to enhance the efficiency of the synthesis reaction. We obtained a pure Cs4PbBr6 perovskite solid within 3 hrs that then realized a high photoluminescence quantum yield (PLQY) of 46%. Furthermore, the Cs4PbBr6 perovskite microcrystal is applied with red emitting K2SiF6 phosphor on a blue-emitting InGaN chip, achieving a high-performance luminescence characteristics of 9.79 lm/W, external quantum efficiency (EQE) of 2.9%, and correlated color temperature (CCT) of 2976 K; therefore, this perovskite is expected to be a promising candidate material for applications in optoelectronic devices.