Structural order in conjugated oligothiophenes and its implications on opto-electronic devices

Over the last ten years, conjugated oligothiophenes have emerged as one of the largest families of organic semiconductors with potential applications in electronics devices. Thin film transistors (TFTs), photovoltaic solar cells, light-emitting diodes (LEDs), light modulators, photochromic switches and laser microcavities are some examples of devices that have been fabricated with oligothiophenes as the active materials. The key advantage of well-defined oligomers over their parent polymers is the high degree of molecular and crystalline ordering they can achieve. Polycrystalline and highly oriented thin films can be easily prepared from solution or by vacuum deposition. In many cases it has even been possible to grow single crystals and elucidate their X-ray structure. The aim of this review is to describe the structure of oligothiophene crystals and thin films and to explore its implications on the performances of various electronic devices.