Interchain interactions in organic pi-conjugated materials: Impact on electronic structure, optical response, and charge transport

The pioneering work of Heeger MacDiarmid, and Shirakawa, rewarded by the 20 00 Nobel Prize in Chemistry, has paved the way for the development of the f ields of plastic electronics and photonics. Functional organic molecular ma terials and conjugated oligomers or polymers now allow the low-cost fabrica tion of thin films for insertion into new generations of electronic and opt oelectronic devices. The performance of these devices relies on the underst anding and optimization of several complementary processes (see sketch). Ou r goal is to discuss, from a theoretical standpoint, the electronic structu re characteristics and interfacial properties that are of importance in all these areas. The concept of interface should be taken here in the microsco pic sense, i.e., molecular interactions among two or several chains/molecul es (of the same or of a different nature). Specifically, we will address th e impact of interchain interactions within an organic layer on the transpor t and optical properties. These issues will therefore be more directly rela ted to transistor and light-emitting diode applications; however, in all in stances, the aspects related to interfacial charge or energy transfer proce sses will dictate the ultimate performance of a material in a given device.