Electronic properties and photovoltaic performance of VONc-ZnO hybrid junction solar cells

In this work, we investigated the effect of the additional layer of zinc oxide (ZnO) nanoparticles to the active layer of Vanadyl-2,3-naphthalocyanine (VONc) solar cells. The two diodes were prepared using conventional thermal evaporation technique to produce ITO/VONc and ITO/ZnO/VONc heterojunctions. The change of capacitance-voltage characteristics showed that ITO/ZnO/VONc cell has a built-in potential (0.85 +/- 0.01 V) higher than that for ITO/VONc cell (0.74 +/- 0.02 V). The dark current-voltage characteristics were recorded for the two diodes in the temperature range of 298-393 K. The rectifier behavior of the two diodes at different temperatures has the same behavior, and ITO/ZnO/VONc cell has a higher rectification ratio. This behavior for two diodes suggests that the dominant forward conduction mechanisms found to be thermionic-emission and space charge limited current mechanisms at low and high applied voltage, respectively. The essential parameters of the diode, such as shunt resistance, series resistance, quality factor, and barrier height, were also calculated. The photovoltaic behavior of two devices has been studied with constant illumination of 80 mW/cm(2) at room temperature. The efficiency of the cell is increased ten times by adding ZnO layer.