  The trap distribution in the conjugated polymer poly(3-hexylthiophene) was
investigated by fractional thermally stimulated current measurements. Two
defect states with activation energies of about 50 meV and 105 meV and Gaussian
energy distributions were revealed. The first is assigned to the tail of the
intrinsic density of states, whereas the concentration of second trap is
directly related to oxygen exposure. The impact of the oxygen induced traps on
the charge transport was examined by performing photo-induced charge carrier
extraction by linearly increasing voltage measurements, that exhibited a strong
decrease in the mobility with air exposure time.
