Studies on electrical and photoelectrical behaviour of ITO/ArV/In Schottkybarrier device

The electrical and photoelectrical properties of aryl viologen (ArV), chemi cally known as 1, 1'-diphenyl-4,4'-bipyridinium dichloride, in the form of thin film, sandwiched between ITO and In electrode were studied. The curren t-voltage (J-V) characteristics in dark show the rectification effect due t o the formation of Schottky barrier at In-ArV interface. The diode quality factor of the device, greater than unity, indicates the recombination of el ectron-hole in depletion region. Ohmic conduction in low voltage range and space charge limited conduction (SCLC)controlled by an exponential distribu tion of traps above the valence band edge, for higher voltage region have b een observed. Various electrical parameters were calculated from the analys is of J-V and capacitance-voltage (C-V) characteristics at different temper atures and discussed in details. At higher frequencies, the device exhibit voltage independent capacitance, which is explained in terms of the extreme ly slow kinetics of space charge and low mobility of charge carriers. The p hotoaction spectra of the device and absorption spectra of the ArV thin fil m reveal that the fraction of light, which is absorbed near or within the d iffusion length of exciton, is responsible for producing the free charge ca rriers. The photovoltaic parameters were calculated from the J-V characteri stics under illumination through ITO and discussed in detail. (C) 1999 Publ ished by Elsevier Science S.A. All rights reserved.