Fabrication of double-walled carbon nanotube film/TiO₂ nanotube array heterojunctions with length-dependent photoresponse for broad band photodetectors

A novel photodetector based on double-walled carbon nanotube (DWCNT) film/TiO₂ nanotube array (TNA) heterojunctions was fabricated, which exhibited high photoresponse in a broad spectral range. The photoresponse of the detector was dramatically dependent on the length of the TNAs. High photocurrent-to-dark current ratio with a value of 3360 was observed in the visible range by optimizing the lengths of the TNAs. The photosensitive regions could be extended into the near-infrared range. These results reveal that DWCNT film/TNA heterojunctions show potential applications for broad band photodetectors.