Dresden 2009 – scientific programme

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SYOP: Symposium Organic Photovoltaics: From Single Molecules to Devices

SYOP 4: Organic Photovoltaics: from Single Molecules to Devices

SYOP 4.61: Poster

Thursday, March 26, 2009, 16:30–19:00, P1A

Investigating aza-bodipy for organic electronics: A chemist's view. — •Roland Gresser, Toni Müller, Horst Hartmann, and Karl Leo — Institut für Angewandte Photophysik, TU Dresden

Current research on organic photovoltaics aims for broader photoactive spectral ranges of the organic solar cells, and the synthesis and investigation of new, appropriate low band gap absorbers are essential.

The focus of this study is on the material class of 4,4-difluoro-4-bora-3a,4a,8-triazaindacene (aza-bodipy) as active donor material in vacuum deposited small molecule solar cells. Due to the straightforward synthesis, an aza-bodipy series with different substituents is prepared and investigated.

All compounds indicate reversible one electron reduction and oxidation waves determined by cyclic voltammetry (CV) in solution. Corresponding absorption measurements show a clear tendency towards a red shift of the absorption maximum with increasing donor strength of the substituents. The origin of this bathochromic shift originates from the increase of the HOMO energy level which was determined by CV.

Additional quantum chemical calculations of the series with ab-initio methods show a typical donor-acceptor charge transfer behavior upon HOMO-LUMO transition. Internal reorganization energies were calculated directly from the adiabatic potential energy surfaces for hole and electron transport process respectively. The results show that aza-bodipy is a suitable material for organic electronics.