Ambipolar Transistor Properties of Charge-Transfer Complexes Containing Perylene and Dicyanoquinonediimines

To investigate charge polarity of transistors based on donor/acceptor cocrystals, charge-transfer complexes of wide donor molecules such as perylene and pyrene are investigated. As-grown single-crystal transistors are deposited from solutions, which attain perfect reproducibility in comparison with the conventional pasted single-crystal transistors. Perylene complexes of dicyanoquinonediimines (DCNQI) with substituents X = CH3, Cl, and Br show hole-dominant ambipolar characteristics. Owing to the large molecular width, the donor/acceptor orbitals are not orthogonal, and ambipolar transport is realized. In contrast, pyrene works similarly to ordinary acenes, and not only the tetracyanoquinodimethane (TCNQ) complexes but also the DCNQI complex show only electron transport. The existence of the short-axis offset in the molecular overlap is the criterion that transforms electron transport to ambipolar transport.