Effect of water vapor on poly(3-methylthiophene)/Mo Schottky diodes

The effect of various atmospheres on the electrical characteristics of Mo/poly(3-methylthiophene) (P3MT)/Pt Schottky barrier diodes was investigated. It is found that the I(V), C(ω) and C(V) characteristics of the diodes are affected mainly by the presence of water vapor and oxygen. The capacitance shows a frequency dispersion characteristic of the presence of deep traps. Peaks are also observed in the C(V) characteristics under forward bias when the diode is subjected to air, oxygen or water vapor. The analysis of the I(V) characteristics shows that the current is space-charge-limited for large biases when the diode is subjected to the various atmospheres. Based upon these results, it appears that the effect of oxygen is to fill the traps and to dope the polymer. The effect of water vapor is manifested by a reduction in the dopant density and a filling of the deep traps. The effect is, however, irreversible in this case.