Electronic and photovoltaic properties of Au/pyronine G(Y)/p-GaAs/Au:Zn heterojunction

Abstract

The electrical and photovoltaic properties of thermally vacuum deposited pyronine G(Y), PYR(G), thin films on GaAs single crystal were investigated. The current–voltage (I–V) characteristic of Au/PYR(G)/GaAs/Au:Zn heterojunction diode under dark condition was measured at different temperatures in the range 298–373K. The device exhibits a rectifying property. The current in the prepared heterojunction was found to obey the thermionic emission model assisted by tunneling in the voltage range (0<V≤0.35volts) while in the voltage range (0.4<V≤1.5volts), the current is space charge limited dominated by single trap distribution. The current–voltage characteristics allow us to evaluate some characteristic parameters such as the series resistance, Rs, shunt resistance, Rsh, ideality factor, n, and the barrier height, Φb. The variation of 1/C2 with voltage shows a straight line at high frequency that indicates the formation of barrier between PYR(G) and GaAs and the potential barrier height is found to be 0.82eV at room temperature (298K). The photovoltaic properties of Au/PYR(G)/GaAs/Au:Zn heterojunction were investigated under illumination by using light intensity of 20mW/cm2 through the finger mesh gold electrode. The short circuit current (Isc), open circuit voltages (Voc), fill factor (FF) and the power conversion efficiency (η) of the device were evaluated from the I–V characteristics under illumination.