Frenkel and Charge-Transfer Excitons in Organic Solids

Publisher Summary This chapter discusses the properties of electronic excitations in organic solids with an emphasis on Frenkel excitons. The chapter describes the microscopic theory of excitons in molecular systems, presents a tutorial example of a molecular dimer, and describes a second quantized notation. The basic properties of the Hamiltonian, Davydov splitting, a microscopic calculation of a dielectric function, exciton polaritons, nonlinear optics, and exciton–phonon interactions are discussed in the chapter. The chapter describes the dielectric theory of Frenkel excitons and demonstrates that this microscopic classic theory of excitons in many respects is very powerful and easier to deal with than a fully quantum mechanical microscopic theory. The diffusive motion of Frenkel excitons in molecular crystals is discussed with special distinction between coherent and incoherent excitons. The most recent applications of Frenkel exciton theory to bio-molecular aggregates, such as those that occur in photosynthetic antenna complexes, are also discussed in the chapter.