Abstract
ABSTRACTDonor-acceptor mixed-stack charge-transfer (CT) compounds can be regarded as a model system for charge carrier separation in molecular-scale donor-acceptor heterojunctions. Here we investigated fundamental photocarrier generation characteristics in single crystals of a donoracceptor mixed-stack system, phenothiazine-tetracyanoquinodimethane (PTZ-TCNQ). The laser beam-induced current (LBIC) measurement on the crystals allowed the discrimination between the exciton and the photocarrier diffusion on the basis of the observed spatial decay profiles. We found that the photocarriers are directly generated by higher-lying CT band excitation and exhibit extremely long diffusion length reaching more than 10 μm. We discuss the origin of the efficient photocarrier generation in terms of the geminate electron-hole pair formation.
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