p-Type doping of tetrafluorotetracynoquinodimethane (F(4)TCNQ) in poly(para-phenylene vinylene) (PPV) derivative "Super Yellow" (SY)

In this paper, we report a case of hole transport in tetrafluorotetracynoquinodimethane doped poly(para-phenylene vinylene) derivative "Super Yellow". The hole mobility of pristine and doped polymer thin films was determined by impedance spectroscopy. The increase in hole mobility upon doping was also verified by current density-voltage measurements. It was found to be increased by two orders of magnitude upon doping. The increase in hole mobility upon p-type doping was explained on the basis of extended Gaussian disorder model by measuring current density-voltage characteristics in the same devices. At low bias, J-V characteristics exhibit clear space charge limited conduction in pristine state but ohmic behaviour when doped. Further, at higher voltages the current density increases non-linearly due to the field-dependent mobility and carrier concentration by filling of tail states of highest occupied molecular orbital of the host material. The room temperature J-V characteristics were well described with the single value of free hole density at low fields. At higher fields it becomes field-dependent followed by a field enhancement factor gamma