Photocarriers generation process and photovoltaic effect in PPHT thin filmSchottky barrier devices

Photogeneration process and photovoltaic effect of Al/poly(3-phenylhydrazon e thiophene) (PPHT)/ITO and In/PPHT/ITO sandwich devices were investigated by measuring steady state photocurrent resulting from illuminating through the ITO electrode. From the comparison of photoaction spectra of the device with the absorption spectra of the PPHT layer, it was observed that PPHT f orms Schottky barrier with In and Al and ohmic contact with ITO. The voltag e dependence of the photocurrent in the vicinity of V-bi was measured at 1 mW/cm(2) of the incident illumination to give the open circuit voltage (V-o c) and short circuit photocurrent (J(sc)). The photoaction spectra of the d evice also suggest that only light absorbed near the blocking contact, i.e. , at Al/PPHT, In/PPHT is effective in producing carriers for external circu it. The dependence of the short circuit photocurrent on the illumination in tensity was also described in detail. Various photovoltaic parameter was al so calculated from the current-voltage (J-V) characteristics of the open de vice under illumination through ITO. (C) 1999 Published by Elsevier Science S.A. All rights reserved.