Electrical, optical and photovoltaic effect in pyronine G (Y) based thin film sandwich devices

The optical, electrical and photovoltaic properties of pyronine G (Y) have been investigated in the form of thin film devices. The molecular system of the pyronine shows the phenomenon of extended conjugation which is in fact responsible for its absorption in the longer wavelength, i.e. 540 nm of th e visible spectrum. Pyronine G (Y) was employed in the form of thin film fo r the fabrication of sandwich devices having ITO/pyronine/Al and ITO/pyroni ne/In structures. The present communication deals with the study of optical , electrical and photoelectrical properties of ITO/PYR/Al and ITO/PYR/In de vices by measuring the J-V characteristics in dark as well as under illumin ation and C-V characteristics in dark. The photoaction spectra of the devic es and absorption spectra of PRY thin films were also employed for evaluati ng the photogeneration process in the device. The observations reveal the f ormation of a Schottky barrier at AI-PYR and In-PYR interfaces and ohmic co ntact at the ITO-PYR interface, showing a diode ideality factor greater tha n unity. From the detail analysis of J-V characteristics of the device at d ifferent temperatures, it is found that the position of the Fermi level lie s above the valence band indicating the semiconductivity of PYR as p-type. The photogeneration mechanism of charge carriers in the device involves the dissociation of excitons at AI-PYR and In-PYR interfaces in their respecti ve devices. Various electrical and photovoltaic parameters were also calcul ated from the analysis of experimental results and discussed in detail. The mechanism of the photoconductivity process in the PYR thin film is been di scussed in detail. (C) 1998 Published by Elsevier Science Ltd All rights re served.