ABSTRACT
Organic semiconductors have been studied since the 1940s, and the initial industrial application of these compounds was xerography, a process exploiting their photoconductive properties [1,2]. One class of materials receiving signifi cant attention is that of π-conjugated small molecules, mainly oligomeric structures. These systems exhibit a common feature of having π-conjugated bonds, giving rise to delocalized, fi lled, and empty π-orbitals, which greatly impact their optical and
electrical properties. In contrast to inorganic semiconductors, the solid-state structure of organic semiconductors is based on weak van der Waals and dipole-dipole interactions between neighboring molecules, imparting within them the properties of both semiconductors and insulators. Modern interest in organic-based electronic devices stems directly from the realization that a linear π-conjugated system (doped polyacetylene) was found in the 1970s to exhibit metallic conductivity. Some of the earliest examples of organic compounds fi nding application in electronic components include effi cient organic light-emitting diodes [3] and organic fi eld-effect transistors (OFETs) [4]. However, the potential of active electronic devices such as solar cells, light emitters, and thin-fi lm transistors remained unfulfi lled for decades because organic materials have often proved to be environmentally unstable and far less effi cient than inorganic materials.
