Preparation and optoelectronic performance of 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine-CuS films for photovoltaic applications

Abstract

This work intends to study the effect of the additional inorganic CuS layer between the ITO-contact and the organic 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraaza-21H,23H-porphine (TTBTP). Two junctions of ITO/TTBTP and ITO/CuS/TTBTP were accomplished by the thermal vacuum evaporating technique. The capacitance-voltage characteristics of these two junctions were investigated. It was found that the built-in voltage was reduced from 0.62 to 0.35 V by the additional inorganic CuS layer. Further, the investigation of the dark current density versus the applied voltage at various temperatures emphasizes the influence of the adding inorganic CuS layer in the lowering of Rs , Rsh and n values. Moreover, getting the same value of the diode quality factor (n) at different temperatures for the two junctions suggested that thermionic emission is the adopted theory. Regarding the power-law (J ∼ Vm) relation, the charge transport mechanism is described by the space charge limited current controlled by a distribution of trap levels. The photoelectric study confirms that the additional inorganic layer plays a key role in the increasing of many parameters such as photosensitivity, short-circuit current density, open-circuit voltage, and power conversion efficiency. Increasing the conversion efficiency ten times by the additional inorganic CuS layer will open the doors for developing the fabrication solar cell with low cost, easily synthesized, and high conversion efficiency.