Effect of Ambient Atmosphere on Photoconductivity of TiO2 Nanotube-CuPc Heterojunction

Abstract

In this study, TiO2 nanotube/copper octakisalkylthiophthalocyanine [(C6S)(8)PcCu] heterojunction was prepared, and photoconductivity of the heterojunction was investigated under various ambient conditions. In order to form TiO2 nanotube arrays, Ti foils was anodized in aqueous HF (0.5 wt%) electrolyte. The structure of TiO2 nanotubes was characterized by using X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). The (C6S)(8)PcCu compound was coated on the nanotube arrays by using jet-spray in an inert ambient from a solution of the phthalocyanine in chloroform to obtain TiO2 nanotube/(C6S)(8)PcCu heterojunction device which characterized by SEM. It is found that TiO2 nanotubes filled with (C6S)(8)PcCu, and the photocurrent of Ti/TiO2 nanotube/(C6S)(8)PcCu/Au device under dry air was 1 or 5 orders of magnitude higher than dark current at the same applied bias in the voltage range of -1.5 V to 1.5 V. The ratio (I-i/I-d) of heterojunction device under different conditions is in the order: (I-i/I-d)(dryair) > (I-i/I-d)(atmosphere) > (I-i/I-d)(nitrogen). The oxygen plays a crucial role in the photoconductivity of TiO2 nanotube/(C6S)(8)PcCu heterojunction.