Effect of Dye Energy Level on the Efficiency and Energetics of Spectral Sensitization

Abstract

A series of dyes varying widely in their lowest vacant (LV) and highest occupied (HO) levels were used to study the effect of dye energy level on the efficiency and energetics of spectral sensitization of an iridium-doped Ag(I)Br emulsion. Results from room-air sensitometry and vacuum sensitometry at various temperatures formed a data base on which to assess current theories of spectral sensitization. The oxygen/moisture sensitivity of the spectral response showed an energy-level threshold in concentration dependence. As the dye LV level was farther displaced from the vacuum level, the dye relative quantum efficiency decreased and the spectral activation energy increased, both linearly. Dyes that failed to follow the general trends were strongly aggregating dyes with low LV levels. Quantitative predictions of the direct-electron-transfer model of spectral sensitization were inconsistent with the results.