SCLC Measurements Research Articles

InSe electrical characterization by means of transport parameters

SCLC measurements in single crystals of the layered semiconductor n-type InSe are reported. The measurements were carried out at various temperatures and on samples grown with indium added in excess (from 5 to 10%). The experimental results suggest that the trapping levels location and the charge transport are dependent on the indium excess. Only the samples grown with an indium excess of about 5% show the features typical of intrinsic semiconductors. The anomalous behaviour of samples grown with indium excess between 6 and 10 is explained by means of scattering mechanisms between charge carriers and ionized impurity centers.

Photoelectrical properties, energy level spectra, and photogeneration mechanisms of pentacene

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 = 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. [Russian Text Ignored].

Electroluminescence in Pentacene Doped Anthracene Crystals

Abstract The recombination radiation spectrum and its transient behavior were measured on a pentacene doped anthracene crystal. The recombination radiation spectrum was more sensitive to chemical or physical impurities than optically sensitized fluorescence spectrum. The intensity of both anthracene and pentacene emission was approximately proportional to the current. Anthracene or pentacene emission was found to consist of three components differing by their decay times; component 1 (decay time <10−5s), components 2,3 (decay times in the millisecond region, τ2<τ3). The component 1 was due to singlet excitons generated directly by carrier recombination. The component 2, the decay time of which was 2–3 ms, was due to triplet exciton annihilation, for its decay time was not affected by a reverse bias voltage and was equal to one half of the observed phosphorescence lifetime. The component 3, which was removed by a reverse bias voltage, was due to detrapped-trapped carrier recombination. Pentacene chemical impurity works as carrier traps or tirplet exciton traps. Anthracene lattice defects work as carrier traps. The SCLC measurement showed the existence of an electron discrete trap introduced by pentacene and electron and hole exponential traps. The present experimental results showed het importance of traps in the recombination process in a mixed crystal.