Generation of hot and complex charge carriers due to the interaction between excitons and free charge carriers in molecular crystals

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Abstract
Applying microscopic many-body theory, the consequences of interaction between a free Frenkel exciton and free electron present in molecular crystal are investigated. Two kinds of reactions are possible: (a) a hot electron is created and (b) a complex charge carrier (exciton+electron) is formed. The rate of reaction (a) between singlet exciton and electron in anthracene single crystal is obtained as ∼7×109 sec−1, in agreement with the rate calculated from experiments. The possibility of reaction (b) is attributed to the net attractive potential of interaction between the exciton and electron. Such a potential of interaction is rigorously derived and its quantitative nature is calculated in pure as well as in mixed crystals. It is shown that the complex charge carrier moves throughout the crystal via hopping from one molecule to another. Competitive importance of both reactions (a) and (b) is discussed.