Photovoltaic and electrical investigation of In/WOx/CuPc/In heterojunctions with light intensity-dependent NDR behaviours

A peripherally tetrachalcone substituted copper(II) phthalocyanine was achieved by cyclotetramerization of the phthalonitrile in the presence of anhydrous CuCl2. The modified CuPc was thermally coated on WOx thin films from which a In/WOx/CuPc/In heterojunction was obtained. The surface of the thin films was investigated using scanning electron microscopy (SEM), where energy dispersive X-ray spectra (EDX) was used to confirm chemical structure. The crystal structures of the thin films were characterized using X-ray diffractometry (XRD). To determine the photovoltaic properties of the heterojunction, I-V plots were obtained under dark and various levels of illumination. It was seen that the heterojunction was responsive to the external light. Using the I-V plots, different diode parameters such as ideality factor, barrier height, series resistance, etc., were calculated. These plots also revealed that the In/WOx/CuPc/In heterojunction exhibits negative differential resistance (NDR) characteristics. Photodiode characteristics indicate that the heterojunction exhibits self-powered photodiode behaviours. It was seen that In/WOx/CuPc/In heterojunctions are sensitive to the external light that photovoltaic characteristics alter when the light intensity alters. However, no clear relation between the light intensity and photovoltaic characteristics were evidenced.

Automated summary

A copper(II) phthalocyanine with a tetrachalcone substitution was synthesized through cyclotetramerization of phthalonitrile using anhydrous CuCl2. The resulting CuPc was thermally coated on WOx thin films to form an In/WOx/CuPc/In heterojunction. The thin film surface was characterized using SEM and EDX, while XRD was used to determine the crystal structure. I-V plots under dark and various illumination levels showed that the heterojunction exhibited photovoltaic properties. The heterojunction also showed negative differential resistance (NDR) characteristics and self-powered photodiode behaviors.