A Fully Transparent, Flexible, Sensitive, and Visible-Blind Ultraviolet Sensor Based on Carbon Nanotube–Graphene Hybrid

Transparent and flexible UV sensors have attracted considerable attention for use in portable/wearable optoelectronic systems. Although UV sensors based on photoactive nanomaterials have been reported for such applications, achieving full transparency and flexibility remains a challenge because they still rely on opaque or brittle electrodes. Here, a fully transparent, flexible, and highly sensitive UV sensor based on 1D carbon nanotubes (CNTs)–2D graphene hybrid is demonstrated. Under UV illumination, oxygen molecules on the CNT surfaces are desorbed by photoinduced plasmon energy, leading to a significant decrease in hole concentration, and correspondingly an increase in the electrical resistance of CNT. The combination of CNT and graphene minimizes the effect of contact resistance and facilitates effective charge transfer between them without potential barrier, resulting in a high photoresponse, which is 30 times as high as that of Au-electrode-based CNT sensor. Simultaneously, CNT–graphene UV sensor shows remarkable transparency (over 80% at 550 nm) and outstanding mechanical flexibility without any significant change in electrical resistance for 500 cycles at a bending radius of 5.5 mm. The integration of CNT–graphene hybrid onto flexible substrates through scalable microfabrication is expected to provide exciting opportunities for the development of high performance, optically and mechanically invisible optoelectronic devices.