In the past few years ?-conjugated polymers (CP) have attracted considerable interest owing to their high potential for applications in novel optoelectronic devices, such as organic light-emitting diodes, solar cells, organic lasers, and ink-jet printed electronic circuits (“plastic electronics”). Since nearly all applications of CPs exploit charge and/or excitation energy transfer within the active organic layer, a detailed understanding and knowledge of the key parameters, that govern these processes, is crucial. The efficiency of charge- and energy-transfer processes in CPs is strongly determined by the electron-phonon coupling strength as well as the energies of the vibrations that couple to the electronic states. However, the inherent pronounced structural disorder in this class of functional materials prevented a direct determination of these parameters as yet. Here it will be shown that single-molecule spectroscopy in combination with pattern recognition techniques for data analysis allows to retrieve the profile of the electronic spectrum and concomitantly the electron-phonon coupling strength in a ladder-type conjugated polymer [methyl-substituted ladder-type poly(para-phenylene), (MeLPPP)]. From these data a weak electron-phonon coupling for this polymer at low temperatures is found. Moreover, there is strong evidence that the low-energy vibrational modes, which are coupled to the electronic transitions, stem from vibrations of the surrounding host matrix indicating an even weaker intra-chain electron-phonon coupling in MeLPPP.


Wednesday, 14^th of May, 17:00h. Conference Room