Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 40: POSTERS Electronic and Optical Properties

CPP 40.10: Poster

Thursday, March 26, 2009, 17:00–19:30, P3

Femtosecond Transient Absorption of a Polyfluorene Copolymer at High Hydrostatic Pressure — •Sebastian Albert-Seifried — Cavendish Laboratory, University of Cambridge, J. J. Thompson Avenue, Cambridge CB3 0HE, United Kingdom

Organic light emitting diodes (OLED) are currently considered low-cost alternatives to established illumination and display technologies. However, the two main problems faced by OLED technologies are short device lifetime and low energy efficiency. To address these shortfalls, it is critical to understand the photophysics of conjugated polymers in the solid state, which are often more complex than in their inorganic counterparts due to the ill-defined interaction of neighbouring molecules.

Applying high pressure is a clean reversible way to increase the interchain interactions and thus study their effects on conjugated polymers. For this purpose, a technique was developed to study ultrafast dynamics of excitation under hydrostatic pressure up to 90 kbar by transient absorption over the whole visible spectrum. In thin films of poly(9,9-di-n-octylfluorene- alt-benzothiadiazole) (F8BT) at high hydrostatic pressure, a strong dynamic relaxation of the stimulated emission by around 200meV was found after excitation. Further, a sharp decline of stimulated emission and photoluminescence with increasing pressure was measured. The pressure dependent spectrscopy is interpreted in terms of interchain and intrachain effects on radiative and nonradiative processes.