Matière Condensée et Systèmes Electroactifs

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Conférence du Pr. Won-Sik HAN

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Carborane Controlling Emission Properties of Siloles: Design Multiple-Photoemissions and Its Applications to White OLEDs
Mercredi 17 janvier 2018 à 10h00
Campus de Beaulieu / Amphi D. Grandjean

Abstract of the Conference

Carborane Controlling Emission Properties of Siloles: Design Multiple-Photoemissions and Its Applications to White OLEDs

Department of Chemistry, Seoul Women’s University, South Korea

Two regioisomeric silole-carboranes, Si-p-Cb and Si-m-Cb, were prepared and their photophysical properties were successfully regulated by controlling the substitution position of ortho-carborane. By incorporating ortho-carboranes onto the silole (silacyclopentadiene), their emissions in solution state were strongly quenched due to the efficient charge transfer from the silole core to the ortho-carborane groups while their benzene analogues, Si-p-Bz and Si-m-Bz, showed distinctive emissions. The most interesting features of regioisomeric silole-carboranes were found in their solid state photochemistry.
In amorphous phase, Si-p-Cb showed multiple photoemissions with dominant strong emission at 572 nm (CT emission) and weak emission at 500 nm (LE emission) while Si-m-Cb showed single emission at 478 nm (LE emission). In crystalline phase, on the other hand, the major radiative process for Si-p-Cb was changed from CT state to LE state, which showed enormously large hypsochromic shift to 482 nm from 572 nm. The opposite phenomenon was observed for Si-m-Cb, which showed a single emission at 478 nm (LE emission) in amorphous phase and enormously large bathochromic shift to 571 nm in crystalline phase. This demonstrated that the CT states of regioisomeric silole-carboranes can be turned- on or -off. Small modification of the molecular geometries by changing the substitution position strongly affects their excited state properties and hence their emission behaviors. To utilize the unique properties of silole-carboranes, Si-p-Cb was used in the fabrication of single-molecule white OLED devices. The fabricated device showed white emission with CIE coordinates of (0.36, 0.45).

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