Crystalline Al/p-Si/n-AgGaSe2/Au heterojunction device was fabricated by depositing AgGaSe2 thin films at temperature 473 K, onto p-type single crystal silicon wafers with surface orientation (111) and glass substrates. The crystalline nature and the chemical composition of the deposited AgGaSe2 films have been confirmed using both X-ray diffraction (XRD) and energy dispersive X-ray spectrometer (EDX) techniques. The dark current voltage characteristics of the heterojunction diode have been investigated at various temperatures to elucidate the electrical conduction mechanisms. It was found that at forward bias voltages <= 100 my, the current is controlled by the thermionic emission mechanism, whereas, at bias voltages higher than 100 mV, the current is controlled by the space charge limited current mechanism. The reverse current mechanism of the diode is controlled by the carrier generation recombination process in the depletion region. The photovoltaic parameters were determined from the current voltage characteristics under illumination. The built-in potential, effective carrier concentration and barrier height were also evaluated from the C V measurement. (C) 2013 Elsevier B.V. All rights reserved.