The effects of metal impurities in poly[(2,5-bis(3-decylthiophen-2-yl)thieno[2,3-b]thiophene] on field-effect transistor properties

We have used particle induced X-ray emission analysis and particle induced gamma-ray emission analysis to determine the elemental impurity concentrations in poly[(2,5-bis(3-decylthiophen-2-yl)thieno[2,3-b]thiophene] samples that have undergone different washing and extraction procedures to remove impurities. Field-effect transistors (FETs) were fabricated from the materials and their electrical characteristics show no significant differences between the devices made from different material samples. Reducing the metal residue levels below the ones measured in the starting material (300 mg/kg Fe, 7 mg/kg Zn, 3000 mg/kg Pd and 12000 mg/kg Sn) does not improve the FET performance. This suggests that it is not necessary to completely remove metal residues in the polymer for FET applications.