Structural and electrical properties of thermally evaporated cobalt phthalocyanine (CoPc) thin films

TLDR: In this article, the mean free path of charge carriers in CoPc thin films and bulk resistivity was estimated using the CBH model with centers of intimate valence alternation pairs type with a maximum barrier height of 1.594 eV.

Abstract: Thin films of CoPc of various thickness have been deposited onto glass substrates using thermal evaporation technique at room temperature. The dark electrical resistivity measurements were carried out at different temperature range (298–423 K). An estimation of mean free path () of charge carriers in CoPc thin films and bulk resistivity, was attempted. Measurements of thermoelectric power confirm that CoPc thin films behave as p -type semiconductors. The ac conductivity ( σ ac ) has been investigated in the frequency range (10 2 –10 6  Hz) and temperature range (298–407 K). σ ac is found to be proportional to ω s where s ≈ 0.879 which is frequency and temperature independence. The ac conductivity interpreted by the correlated barrier hopping (CBH) model with centers of intimate valence alternation pairs type with a maximum barrier height, W M ≈ 1.594 eV.