Optical Properties, Conductivity and Structure of the DTT-TCNQ CT Complex

Abstract

Abstract The crystal structure, the optical spectra and electrical conductivity of dithieno(3,2-b; 2′,3′-d)thiophene-tetracyanoquinodimethane (DTT-TCNQ) charge-transfer complex have been measured. DTT-TCNQ crystallizes in the monoclinic space group P21/c with a = 7.206(2), b = 7.574(2), c = 32.324(9), β - 92.18(4)°, Z - 4, and the donor and acceptor molecules are arranged in alternated stacks. The low conductivity (a = 10−2 S cm−1 for the single crystal, along the stacking axis a) is characteristic of a semiconductor with activation energy of .61-.76 eV, and is related to the alternate stack structure. Despite the poor condctivity of the DTT-TCNQ CT complex we estimated, from structure and IR data, a low degree of ionicity (p = .2–.3) which characterizes the DTT molecule as an interestign donor. The polarized IR spectra shows the effect of vibronic activation of some of the ag modes of TCNQ.