The main optical, dark and photoconductivity, photo‐emf, and photoemission characteristics are studied for thin‐layers of pentacene (Pc) crystals. It is shown that in the h = = 2.2 to 4.0 eV spectral region intrinsic photogeneration is dominant in Pc crystals, presumably proceeding via an autoionization mechanisms with a threshold value Ec = = (2.20 ± 0.05) eV. Whereas in the hvv = 1.4 to 2.2 eV spectral region an exciton photogeneration mechanism, namely, generation of excess charge carriers through triplet exciton‐trapped hole interaction, seems most probably. The energy level spectra of neutral and ionized states of the Pc crystal are determined. The Pc crystal ionization energy Ic equals to (5.07 ± 0.05) eV; the forbidden energy gap ΔE0 = (2.20 ± 0.05) eV; the intrinsic dark conductivity activation energy E a0 = ΔE0/2 = (1.15 ± 0.15) eV. The electron affinity Ac of the Pc crystal, determined by three independent methods equals to (2.87 ± 0.10) eV, (2.70 ± 0.15) eV, or (2.73 ± 0.2) eV, respectively. The characteristic energies of the quasi‐continuous trap distribution for vacuum evaporated thin Pc crystals layers are kTc = 0.12 eV in an exponential approximation and ± = 0.28 eV in a Gaussian one as determined from SCLC measurements.

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Measurements are made of the dependence of the electrical current on voltage and sample thickness for thin layer systems of some molecular associates (MA) with intermolecular hydrogen bonds. The results show that the MA under investigation may be divided into two groups with respect t o the mechanism of charge carrier generation in high electrical field ( E = lo4 to lo6 V/cm). For the first group of MA, the ohmic region of C-V characteristics is followed by a non-linear injection region of space charge limited current (SCLC) type with a quasi-continuous exponential trap distribution, A t higher electrical fields ( E > lo5 Vjcm) the injection region passes t o the dominating bulk ionization region.For the second group of MA the bulk ionization region follows directly after the ohmic region. The main experimental criteria of both mechanisms are discussed.