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The increase of the electrical conductivity of the arylenevinylene (AV) system 1,4-bis[2-(3,4,5-trimethoxyphenyl)ethenyl] benzene was measured as a function of the doping level of iodine. Compressed powders and films blended with polystyrene (PS) containing up to 30 wt.% of the oligomer were used. At the highest doping level the conductivity of the compressed powder reaches a value of 3.3×10−4 Ω−1 cm−1. The conductivity, measured between 90 and 300 K on the powder with the highest conductivity, is thermally activated with an activation energy of ∼0.1 eV. The thermopower is positive in agreement with a charge transfer from the organic chain to an iodine atom. Its value is small (25 μV K−1) and temperature independent. The results are interpreted in terms of small-polaron hopping. [Copyright &y& Elsevier]

Cu(II)-dithiooxamide polymers were prepared by a direct deprotonation of the ligand with a Cu(II) salt. The polymers had a chain length of about 13 units. The undoped polymers showed low electrical conductivity with an Arrhenius-type temperature dependence. Doping of Cu(II)-N,N′-dimethyldithiooxamide was performed by iodine in the vapour phase and by FeCl3 in solution. In both cases, the oxidative doping resulted in highly increased conductivities. A thermopower measurement indicated p-type conduction. The infrared spectra of the undoped material and the one doped with FeCl3 were completely identical, indicating that charge transfer from the ligand to the dopant is small. The conductivity curves of the doped polymer did not show an Arrhenius-type behaviour. In order to find an explanation for the conduction mechanism different models were tested. The best fit of the experimental conductivity data of the FeCl3-doped polymers was obtained with the theoretical prediction of a variable-range hopping model. [Copyright &y& Elsevier]

Abstract: The effect of temperature and composition on the I–V characteristics of blends of (poly(2-methoxy-5-(2′-ethyl-hexyloxy)-l,4-phenylene vinylene) (MEH-PPV), and (6,6)-phenyl-C61-butyric acid methyl ester (PCBM) sandwiched between a transparent indium tin oxide (ITO) electrode and an Al backside contact (solar cell structure) are investigated. The observed dark I–V curves agree well with the trap-controlled space charge limited transport theory. The illuminated I–V curves do not obey the theory of space charge limited currents. The short-circuit currents in the illuminated samples depend strongly on the composition. The current is maximum for the 80% PCBM concentration in the blend. The open circuit voltage also depends on the composition. It is maximum for 0% PCBM concentration and decreases monotonically with PCBM concentration. This might lead to the conclusion that the open circuit voltage is due to internal bulk heterojunctions (BHs). However, we have pointed out that this conclusion, arrived at by earlier workers also, is not necessarily valid. The superposition principle is not valid but the discrepancy is small. [Copyright &y& Elsevier]