Phthalocyanines carrier trapping

In the early 1950 s it first became possible to determine the photoelectric sensitivity of dyes of different classes (phthalocyanines, cyanines, etc.) by measuring barrier-layer photopotentials in cases where barriers were strongly affected by carriers trapped in the surface states of adsorbed gases 54-56>. Jn agreement with the theory of inorganic surface-barrier rectifiers, asymmetric current-voltage curves were also observed. 

---