Electronic Properties of Branched Molecular Structures Review

Abstract

The design of new types of macromolecular architecture is one of the main directions in the development of modern polymer physics. As applied to electronics, electroconductive π-conjugated molecules occupy a special place. In this review, the distinctive features of the electronic properties of organic semiconductors when compared with their solid-state analogs are considered. Special attention is paid to the role of electron–electron and electron–phonon interactions in the formation of self-localized excited states, i.e., solitons and polaritons. The constructive and destructive interference effects in molecular structures containing branching nodes and ring groups are discussed. The size of a branched molecule should herewith be small to conserve quantum coherence. Self-localization effects in such molecules are insignificant and transport is determined by electrons and holes injected from contacts. Two approaches to the description of quantum interference in branched molecules are proposed, notably, based on molecular orbitals and in the scope of the pattern of localized atomic orbitals. These approaches make it possible to formulate design rules for molecular structures, in which interference is observed. The latest results on the design of quantum-interference molecular transistors with ultralow energy consumption are presented. Nonconjugated tree-branched polymers, so-called dendrimers, which can be efficient for designing systems of the collection and transformation of electromagnetic radiation are briefly considered.