Study of the electrosynthesis of poly(3-butylthiophene) and its semiconductor properties

The mechanism of the electrosynthesis of poly(3-butylthiophene) (PBuT) was studied by cyclic voltammetry and potential step methods in comparison with polybithienyl. The anodic oxidation polymerization of the 3-butylthiophene underwent two steps: oligomer formation and further polymerization to form the polymer. The doping level of the PBuT increases with the cycle number of the potential sweeps during polymerization. The current responses to the potential steps indicate a nucleation and nuclei growth process which is r epeated layer to layer. The differential capacity (Cd) and photocurrent wer e measured at the PBuT films in the aqueous electrolyte solution. The C-d(- 2) VS. E plot shows two regions of linearity, one with a negative slope and the other with a positive slope in different potential regions, which give the same flat-band potential. This indicates that the PBuT film exhibits b oth p-type and n-type features of a semiconductor at differrent potential r egions. The cathodic photocurrent spectrum was analysed by the (j(ph)h nu)( 2/n) vs. h nu plots, giving band gap energies of 2.41 eV for n = 1 and and 2.01 eV for n = 4.