doi:10.1038/nindia.2010.97 Published online 21 July 2010
Researchers have designed several new semiconducting organogels that contain nanosized wires. The organogels form through self-assembly, have good electrical properties and are expected to be useful for the design of bulk-heterojunction organic photovoltaic devices.
The self-assembly of semiconducting organic molecules in solution and solid substrates on the nanometre scale is essential for the field of organic electronics. In this respect, organic molecules such as thiopene-derived molecular systems look promising.
The researchers first synthesized five trithienylenevinylenes (TTVs), a type of thiophene-derived organic compound. Through liquid-phase epitaxy, a method for producing semiconducting crystal layers, they dissolved the TTVs in a variety of organic solvents — chloroform, decane, benzene and toluene. This gave rise to self-assembled gels of TTVs.
Of all the TTVs functionalized with amide groups, TTV4 and TTV5 formed stable organogels. Films of TTV4 and TTV5 prepared from decane–chloroform solutions exhibited high charge-carrier mobility when compared with films obtained from chloroform solutions.
The fibres in TTV4 assemblies were several micrometres long, with an average width of 120 nm and a near-uniform height of 10–15 nm. The interconnected fibres in TTV5 had a width of 50–150 nm and a varying height of 4–10 nm.
"This work is unique in the sense that the self-assembled TTV gels showed enhanced electronic properties," says lead researcher Ayyappanpillai Ajayaghosh.
The authors of this work are from: Photosciences and Photonics Group, Chemical Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, Trivandrum, India; Graduate School of Engineering, Osaka University, Suita, Osaka; and PRESTO, Japan Science and Technology Agency (JST), Japan.