Research team led by Professor Kim Bo-hyun and Chun Seok-woo of KAIST’s New Material Engineering Department made an announcement on the 20th that it has developed a technology that can alternatively express two kinds of light from a single molecule.

Result of this research was introduced through online version of Advanced Materials that is a scientific journal for new materials.

This technology can be used widely in variety of fields such as HD TV, bio, optical communication and others.

Principle of every material emitting light is identical. Energy that is created as electrons that are in ground state rise to excited state and return to ground state again becomes either heat energy or light energy. If ratio of energy changing to light energy is higher than ratio of energy changing to heat energy, it becomes display screen that is frequently seen.

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<Actual element that is layered by graphene-platinum porphyrin complex. KAIST has developed a technology that can express two kinds of light from a single molecule.>

Fluorescence means when excited electrons emit light after going up to high energy state and falling immediately while phosphorescence means when excited electrons emit light after going up to a lower energy state and falling slowly.

To solve this problem, research team used a method where graphene and porphyrin are layered alternately like making a sandwich. Research team used a principle where fluorescence is expressed strongly while phosphorescence is amplified at the same time due to graphene Plasmon (electron vibration in group due to light)and resonance from porphyrin that occur when porphyry, which emits strong phosphorescence, is layered thinly on top of graphene.

Through testing, research team found out that complex of graphene and platinum porphyrin increases fluorescence and phosphorescence up to 29 times and 7 times respectively compared to current platinum porphyrin. Research team was able to prove that increase of light strength by controlling number of graphene layers and controlling ratio of light emitting from fluorescence and phosphorescence are possible.

Display’s flexibility and efficiency of circuits increase because more than two 2 kinds of color can be expressed from a single molecule if complex of flexible graphene and porphyrin is used. Number of matters that are used to express many colors within TVs can be reduced by more than half.

“Until now, we thought that it was impossible to alternatively express two kinds of light from a single molecule due to quantum mechanics and photochemistry.” said Professor Kim.

Daejeon = Staff Reporter Park, Heebum |