T. Piok

Solution Processed Conjugated Polymer Multilayer Structures for Light Emitting Devices

We study the feasibility of semiconducting polymer nanospheres deposited from miniemulsions as an approach to form organic multilayer structures and devices from an all solution based process. A detailed study of the wetting and film forming properties of the dispersed semiconducting polymer nanospheres on different polar and non-polar organic surfaces is given. The transmission and fluorescence properties of the polymer multilayer structures are studied. Organic light emitting devices based on such multilayer structures are presented and their properties are discussed.

The influence of keto defects on photoexcitation dynamics in polyfluorene

Abstract The optical properties of two differently substituted types of polyfluorenes, 9-monoalkylated PF (mono-PF) and 9,9-dialkylated PF (bi-PF) where studied by means of photo-induced absorption (PIA) and ultrafast pump and probe measurements. The photo-induced absorption was complemented by measurements on a fluorene–fluorenone copolymer, which can be seen as a model substance for the polyfluorenes containing keto-defect sites. By differential transmission measurements we show that for the 9-monoalkylated PF measurements the singlet and triplet signal is strongly reduced compared to the 9,9-dialkylated PF. Instead, the polaron signal becomes the dominant feature.

A detailed study of the photophysics of organic semiconducting nanospheres

Conjugated polymers are an intriguing class of organic semiconductors which can be utilized as active medium in a wide range of electronic applications. Semiconducting polymer nanospheres fabricated from a conjugated polymer dispersed in aqueous phase have been realized successfully utilizing the miniemulsion process. This class of material combines the properties of conjugated polymers and nanostructured matter and can overcome certain limitations in the film formation of defined multi-layer structures and self assemblies and can, therefore, enable new device design concepts. We present first spectroscopic investigations to characterize nanospheres of methyl-substituted ladder-type poly( para-phenylene) in film and compare them to conventional bulk films of the same polymer. The dynamics of the various photo-excited states is probed via both steady state and transient differential transmission spectroscopy.