Abstract

The growing interest in semiconducting polymers as device materials ¹-³ for applications such as thin films transistors, light-emitting diodes, lasers, and photodectors has also stimulated theoretical and experimental interest in low-dimensional organic semiconductors. ⁴-⁸ It is expected that organic quantum wells, quantum wires, quantum boxes, and superlattices may exhibit strong excitonic effects and large exciton binding energies [~0.5 -1.0 eV] in part because of the relatively small dielectric constants of organic molecules and polymers [~3 - 4].⁴-⁶ In spite of the many theoretical studies which have predicted quantum confinement effects in heterostructured semiconducting polymers,⁵,⁶ clear experimental observation of such effects was not reported until very recently. ⁹,¹⁰ One major experimental difficulty is the rather small exciton Bohr radii (a_B) in bulk organic semiconductors (a_B~1.0 - 1.5 nm) which places severe limitations on suitable techniques for preparing the nanoscale structures.¹⁰,¹¹

© 1997 Optical Society of America