Diffusion photovoltage in poly(p-phenylenevinylene)

Photovoltage phenomena in poly(p-phenylenevinylene) (PPV) are investigated under pulsed laser illumination. The photovoltage transients are strongly r etarded in time depending on sample thickness, laser intensity, and bias il lumination. It is shown that the photovoltage in PPV originates from separa tion of excess electrons and holes due to their concentration gradient and different diffusion coefficients (diffusion photovoltage). The diffusion co efficient of excess holes is found to be on the order of 1x10(-6) cm(2)/s a nd it increases with increasing excitation intensity and intensity of bias illumination. The diffusion coefficient of excess electrons is about 1-2 or ders of magnitude smaller than for excess holes. (C) 2001 American Institut e of Physics.