Photoelectro-chemical properties of anilino squaraine derivatives in LB films

Photocurrent generation from Langmuir-Blodgett (LB) overlays on indium tin oxide (ITO) electrodes, where the active components are 2,4-bis[4-(dibutylamino)-2-hydroxyphenyl]squaraine (1) and the unsubstituted analogue, 2,4-bis[4-(dibutylamino)phenyl]squaraine (2), have been investigated. Dye 1 shows improved behaviour compared with the latter and differences in performance are attributed to a modified aggregate structure, this being indicated by variations in the LB film spectra. The photocurrent generation is enhanced by the presence of electron accepters, e.g. N,N'-dimethyl-4,4'-bipyridinium diiodide (MV2+), but quenched by electron donors, e.g. hydroquinone (HQ). The concentration dependence is reported.