High-performance photoresponse from single-walled carbon nanotube–zinc oxide heterojunctions

Photoactive materials consisting of single-walled carbon nanotube (SWNT)–zinc oxide (ZnO) heterojunctions targeted for optoelectronic applications are investigated in terms of photoresponse and photovoltaic effects. The devices based on SWNT–ZnO heterojunction films are fabricated by two step processes: first, a well aligned SWNT monolayer is deposited on an oxide substrate by the Langmuir–Blodgett (LB) technique; then a ZnO film prepared by filtration of ZnO nanowire solution is transferred onto the SWNT film to form SWNT–ZnO junctions. The SWNT–ZnO heterojunction demonstrates faster photoresponse time (2.75 s) up to 18 times and photovoltaic efficiency (1.33 nA) up to 4 times higher than that of only a ZnO device. Furthermore, the mechanisms of UV sensitivity enhancement and photovoltaic effects are explained according to the high electron mobility in the SWNT–ZnO heterojunctions.