The contact potential difference between cadmium sulfide and the sensitizing dyes pinacyanole, kryptocyanine, and neocyanine has been measured by the electron beam retardation method and found to be of the order of 0.3 v in each case. That between silver bromide and pinacyanole has also been measured to be 0.38 v, the dye in all cases having the smaller electron affinity. These results confirm the tenability of the Gurney-Mott electron transfer mechanism of dye sensitization in photography. Using the same method the electron affinity of pinacyanole has been found to be about 3.1 ev; that of silver bromide is thus approximately 3.5 ev, in agreement with previous estimates.
R. C. NELSON, "Contact Potential Difference between Sensitizing Dye and Substrate," J. Opt. Soc. Am. 46, 1016-1019 (1956)