Electrochromic diffraction from nanopatterned poly(3-hexylthiophene)

Poly(3-hexylthiophene) (P3HT) films were patterned by a soft lithography technique using a nanopatterned polydimethylsiloxane (PDMS) mold to generate one-dimensional (1D) grating and two-dimensional (2D) crossed line pillar patterns. The redox currents (i(p)) were significantly increased due to the facilitated diffusion of ClO4(-) counterions associated with redox processes at the P3HT electrode as analyzing cyclic voltammetry (CV) was performed at different scan rates (ν). It was found that the diffusion coefficient (D(f), cm(2) s(-1)) for ion diffusion in the patterned electrode was much larger than that of the pristine P3HT electrode. Furthermore, the value of D(f) in the 2D electrode was three times higher than that in a pristine film. As a result of such facilitated charge transport, the electrochromic (EC) properties of the patterned P3HT electrode were greatly enhanced and dependent on the dimension of the pattern. Thus, the electrochromic efficiency (E(e)), including the coloration (E(c)) and bleaching efficiencies (E(b)), was higher as the dimension of the pattern was increased; E(e) was maximized in the 2D patterned P3HT film. In a patterned cell, electrochromic diffraction was reversibly observed with a switching efficiency (R(DE)) of 2 and 2.5 for the 1D and 2D patterned cells, respectively.