Factors Which Control the "N-Type" or "P-Type" Photoelectrical Behavior of Molecular Semiconductor Thin Films

Thin crystalline films of phthalocyaninatozinc(II) (PcZn), and its derivatives tetrapyridotetraazaporphyrinatozinc(II) (TPyTAPZn) and naphthalocyaninatozinc(II) (NcZn); as well as of perylenetetracarboxilic dihydride (PTCDA) and its derivative dimethylperylenetetracarboxilic diimide (MePTCDI), have been prepared by vapor deposition under UHV conditions. The electrical conductivity (σ d ) and photoconductivity (σ p ) of these films were measured on interdigitated microelectrode arrays (IMA) of PtSi x on Si. The films were studied as prepared and during exposure to rising partial pressures of oxygen and ammonia. Changes of σ d and σ p with O 2 or NH 3 exposure, as well as changes in their activation energies E A , showed striking differences among the studied compounds