Topic: Dyes and Pigments for Organic Electronics & Photovoltaics
Speaker: Prof. Frank Würthner, Universität Würzburg
Time: 15:00, April 13, 2017
Venue: Room N308A, Building of State Key Laboratory of Luminescent Materials and Devices, Wushan Campus
Abstract:
In recent years we could witness a shift of paradigm in organic semiconductor research towards dyes and color pigments. Thus, after two decades of research focused on conjugated polymers and oligothiophene as well as acene based organic semiconductor molecules most recent work in several laboratories demonstrated high charge carrier mobilities > 1 cm2V-1s-1 for various classes of dyes and pigments. These results are remarkable owing to the presence of dipolar functional groups in these compounds which was believed to result in large reorganization energies and bad transport properties. Obviously this view needs to be reassessed. In particular for organic photovoltaics the success of several low band gap conjugated oligomers and polymers (containing dipolar functional groups) as well as small molecule based organic colorants appears highly promising.
In this lecture I will give an overview on our work on n-type organic semiconductors based on naphthalene and perylene bisimides and p-type organic semiconductors based on merocyanines, squaraines and diketopyrrolopyrroles. A particular focus will be given on the most unusual highly dipolar merocyanine dyes which exhibit outstanding performance in bulk heterojunction solar cells with PCE > 6%. Our recent demonstration of hole mobilities up to 1.3 cm2V-1s-1 in organic thin film devices and up to 8.6 cm2V-1s-1 in organic single crystals clearly corroborates the view that the presence of dipolar groups does not imply bad transport properties. Dyes and colorants are accordingly very versatile for organic electronics and organic photovoltaics.