Influence of Centrifugation on the Conductivity of Poly-N-Epoxypropylcarbazole — Copper Phthalocyanine Films Deposited from Solution

Abstract

We investigated the electrical conductivity of films composed of two photosensitive organic semiconductors, poly-N-epoxipropylcarbazole (PEPC) and copper phthalocyanine (CuPc, C₃₂H₁₆N₈C_u), which had been deposited from solution at different gravity conditions from 1g to 1107g. Visually, the films grown with centrifugation were more homogeneous. The X-ray analysis of the deposited films indicated a small shift of the characteristic peak for copper phthalocyanine (at 2͘ = 7.10°) as acceleration was increased. The electrical conductivity at 1000 Hz was measured in the range from 300 K to 410 K using a sandwich-type cell. There was a 1.5-fold increase in the conductivity and 2-fold decrease of activation energy with increased acceleration. Scanning electron microscopy (SEM) showed more uniform films at higher accelerations and with larger size of agglomerates. Analysis of the conductivity measurements indicated the presence of a compensative effect that manifested itself as a linear increase of activation energy with the logarithm of the pre-exponential factor.