Regensburg 2010 – scientific programme

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DS: Fachverband Dünne Schichten

DS 16: [CPP] Organic Electronics and Photovoltaics I (Joint Session DS/CPP/HL/O)

DS 16.4: Talk

Tuesday, March 23, 2010, 10:15–10:30, H37

Structure property relationship in aza-bodipy absorber materials for organic photovoltaics — •Roland Gresser, Toni Mueller, Moritz Philipp Hein, Karl Leo, and Moritz Riede — Institute of Applied Photophysics, Dresden University of Technology, Germany

In this joint experimental and theoretical study, we focus on the structure property relationship of aza-bodipy dyes as active donor materials in vacuum deposited small molecule solar cells.

The position of the materials HOMO can be intentionally varied by the choice of the functional group attached to the molecule. The absorption spectra show a red shift of the maximum with increasing donor strength of the substituents due to the increasing HOMO energy and decreasing band gap.

Based on crystal structure data, the charge carrier mobility determining parameters like reorganization energies and transfer integrals are calculated. The results show an increasing molecular orbital overlap and significant higher transfer integrals upon planarization and rigidification of the molecule. With this information, the observed charge carrier mobility differences from experiment can be explained.

In addition to the electronic properties a high thermal and photo stability is essential. From combined thermogravimetric analysis and mass spectroscopy we could determine the degradation process of the material and were able to increase the thermal stability by substitution of the involved species.