Adv. Mater. 24, 2305–2309 (2012)

Credit: © 2012 WILEY

Sunlight in the ultraviolet-A (UV-A) range of 320–400 nm is only weakly absorbed by the Earth's atmosphere and is known to contribute to an increased risk of skin cancer. Today's photodetectors for the UV-A range — devices typically based on ZnO and ZnS — generally exhibit slow response speeds, weak photocurrent and poor stability. Xiaosheng Fang and co-workers in China have now developed a UV-A photodetector based on single-crystalline ZnS–ZnO nanobelts that provides tunable spectral selectivity and a wide photoresponse in the UV-A range. The researchers say that the optimized performance of the device is much better than that of pure ZnS or ZnO nanostructures because it combines high sensitivity with a large external quantum efficiency and very fast response speed. The photodetector could prove useful for applications such as high-frequency optical communication, memory and optoelectronic circuitry.