ELECTRODE-LIMITED PHOTOINJECTION AT METAL-POLYMER INTERFACE

The pulse photoconductivity in thin films of poly(methylphenylsilylene) with different electrodes was investigated as a function of electric field (F) and temperature (T) by the time-of-flight method. The electric field dependences of the apparent quantum efficiency (eta) were analysed in the frame of electrode-limited photoinjection. For the samples irradiated through the ITO electrode, eta followed the relation eta=eta(0) exp(-bF(-1/2)), where eta(0) and b are constants. For the irradiation through the gold electrode, the electrode-limited photoinjection was not so strong and at higher electric fields Schottky emission prevailed; the electric field dependence of the photogeneration efficiency was given by the relation eta=eta(0) exp(aF(1/2)-bF(-1/2)), where a and b are constants. The hole diffusion length was found to be in the range 1.8-6 nm, being longer for samples irradiated through gold electrodes.