Effect of light on the poly-3-phenylthiophene properties

The electrochemical and photoelectrochemical behavior of a conducting polym er, poly-3-phenylthiophene (P3PhT), is studied in acetonitrile containing s alts of tetrabutylammonium (TBA) and lithium. Like other thiophene polymers , P3PhT may or may not be doped cathodically in the presence of salts of TE A or lithium, respectively. In general, the photoelectrochemical behavior o f P3PhT resembles that of polybithiophene and poly-3-methylthiophene. In pa rticular, P3PhT is photoactivated when exposed to light at negative potenti als. Depending on the system in which measurements are taken tin the presen ce of salts of lithium or TEA), P3PhT undergoes photoelectrochemical undopi ng or photoelectrochemical cathodic doping, respectively, which is confirme d by measuring electrochemical impedance. However, the photoelectrochemical processes on P3PhT Cat least in solutions containing lithium salts) procee d much slower than those on other thiophene polymers we studied earlier. Th e concentration of doping ions in P3PhT in the presence of lithium salts is higher than that in the presence of TEA salts even in the undoped state. T his is due to a specific interaction between Lif and the phenyl group in P3 PhT.