Copper Phthalocyanine Nanowire Based Solar Cells

Abstract

AbstractPhotovoltaic devices based on organic semiconductors are of interest because of their potential as flexible, lightweight and inexpensive devices. One of the promising devices, involves the heterojunction between copper phthalocyanine (CuPc) and 3,4,9,10-perylenetetracarboxylic bis-benz-imidazole (PTCBI). Earlier, we reported, the highest Voc (1.125V) in a single organic heterojunction solar cell in an ITO/PEDOT:PSS/CuPc/PTCBI/Al structure. Results were interpreted in terms of a modified CuPc-Al Schottky diode for this thin PTCBI layer case and a CuPc-PTCBI heterojunction for the thick PTCBI case. We also reported the device characteristics of Copper phthalocyanine (CuPc)/Aluminum (Al) Schottky diode solar cells. Here, open circuit voltages (Voc) increased from 220 mV at 15 nm to 907 mV at 140 nm. Analysis of the current-voltage characteristics indicated that tunneling and interface recombination mechanisms are important components of the current transport at the CuPc/Al junction. With the objective of higher short circuit current densities in mind, we have extended our earlier work on organic semiconductors to nanowire based designs. In this paper, we report the fabrication, materials and electrical characterization of CuPc nanowire based solar cells in AAO templates by electro-deposition. The CuPc nanowires were electrochemically deposited into the AAO templates using CHCl3 (Chloroform) containing 10-4 M CuPc with 0.5 ml of CF3COOH (Trifluoro acetic acid). The nanowires were characterized by XRD, UV-Vis absorption spectroscopy, electron microscopy and electrical measurements. CuPc nanowires were also electrodeposited onto ITO/glass substrates and compared with templated nanowires for their structural, optical and electrical properties. Effect of the PEDOT: PSS buffer layer on the nanowire based device characteristics was also investigated.