ENERGY-GAP DEPENDENCE OF EFFICIENCY OF PHOTOINDUCED ELECTRON-TRANSFER FROM CYANINE DYES TO SILVER BROMIDE MICROCRYSTALS IN SPECTRAL SENSITIZATION

The relative quantum efficiency (ør) ranged from less than 0.01 to unity for the photoinduced electron transfer from sensitizing dyes (cyanine dyes) to silver bromide microcrystals in the spectral sensitization of a photographic system. The energy gap dependence of the electron transfer has been examined in terms of the dependence of ør upon reduction potentials of dyes and has revealed that the electron transfer takes place according to Marcus theory with a small rearrangement energy (0.05 eV) and without the inverted region. A mechanism has been proposed for hole-trapping supersensitization to improve ør of poorly sensitizing dyes. © 1990 American Chemical Society.