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1 Materials Science Poland

1 2007

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Mechanism of charge generation and photovoltaic effects in lead phthalocyanine based Schottky barrier

Sharma G. D., Choudhary V. S., Janu Y., Roy M. S.

Materials Science Poland

2007

Vol. 25, No. 4

1173--1191

Photovoltaic properties of lead phtalocyanine (PbPc) thin films sandwiched between indium tin oxide (ITO) and aluminum electrodes (ITO/PbPc/Al) have been investigated. The J-V characteristics of the device reveals that current flow across the device is limited by hole injection at Al/PbPc below 300 K, wherein Al is kept at higher bias. Junction parameters such as built-in potential (Vbi), carrier concentration (Na), the width of depletion layer (W) were evaluated from the C-V measurements. The mechanism of transport of carriers in Al/PbPc/ITO has been investigated based on the detailed analysis of current- voltage characteristics at various temperatures in the dark. The PbPc form hole injection barriers with both Al and ITO electrodes which are 0.88 eV and 0.11 eV, respectively, indicating the formation of nearly Ohmic contact with ITO and the Schottky barrier with Al. The photovoltaic parameters of the device have been estimated from the analysis of the current-voltage characteristics under illumination and discussed in detail. Electrically active defects were investigated by the space charge capacitance spectroscopy methods at various temperatures (from 250 K to 350 K) and frequencies (from 5 Hz to 1 MHz), respectively. The activation energy calculated from the capacitance spectroscopy at various temperatures is about 0.32 eV suggesting that the defects originate from the trapping centres at Al/PbPc interface.