Interface properties and electronic structure of new organic low band gap materials

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Low band gap (LBG) polymers are promising candidates for activeorganic layers in opto-electronic devices, such as organic solar cellsor light emitting diodes. The properties of these materials in devicesare strongly influenced by their morphology and ability for selforganizationin thin-films. It was already shown within the first fundingperiod that (additional) alkyl-thiophene moieties can improve distinctlyfilm forming properties in thin films of LBG polymers. A systematicinvestigation of the influence of the introduction of thienylene spacerunits with different substitution pattern in LBG polymer structures onboth electronic properties and the ability for self-organization is thefirst goal of this proposal. The second focus of the joint project is thesynthesis and characterization of new diketopyrrolopyrrole (DPP)-based donor-acceptor co-polymers with a varying degree ofladderization. We will investigate how the degree ofplanarization/ladderization influences the ordering and electronicproperties in thin films. The experimental investigations of thin filmsand interfaces will be carried out using a variety of complementaryspectroscopic and microscopic techniques that shall provide wide anddetailed information on both (interfacial) electronic structure andorganization in thin films. That includes photoemission and variousoptical spectroscopies in addition to atomic force and electronmicroscopy.