Photocarriers generation process and photovoltaic effect in PPHT thin film Schottky barrier devices

Photogeneration process and photovoltaic effect of Al/poly(3-phenylhydrazone 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 forms Schottky barrier with In and Al and ohmic contact with ITO. The voltage dependence of the photocurrent in the vicinity of Vbi was measured at 1 mW/cm2 of the incident illumination to give the open circuit voltage (Voc) and short circuit photocurrent (Jsc). The photoaction spectra of the device also suggest that only light absorbed near the blocking contact, i.e., at Al/PPHT, In/PPHT is effective in producing carriers for external circuit. The dependence of the short circuit photocurrent on the illumination intensity was also described in detail. Various photovoltaic parameter was also calculated from the current–voltage (J–V) characteristics of the open device under illumination through ITO.