Exciton dissociation and mobility in conducting polymers and oligomers

摘要

A survey of the lterature shows that reverse bias current I_L of an illuminated conducting polymer Schottky diode increases with voltage. We suggest that this increase in I_L with applied reverse bias is due to a combination of two factors: 91) increase of mobility, and (2) dissociation of exitions. The experimental results agree with the values of I_L calulated using either of the two mechanisms. Therefore it is difficult to determine the relative importance of the two mechanisms. The relative importance can be determined only if reliable values of material parameters are available. We have fabricated Schottky diodes and FETs using 5-ring n-octyloxy-substituted loigl[p-phenylene vinylene](Ooct-OPV5) and C_(60). SThe mobility of the oligomer derived from the measured characteristics of the diode is 3.29x10~(-7)cm~2/Vs and from the FET data, 3.24x10~(-4) cm~2/Vs. These results show that the mobility (and other material parameters) depend strongly on the structure of the device. Therefore for interpreting the I_L data it is important to measure the material parameters on the same structure on which I_L measurements are made.