Broadband Omnidirectional Light Trapping in Gold-Decorated ZnO Nanopillar Arrays

Abstract

The photoluminescence (PL) and reflectivity characteristics of zinc oxide nanopillars- (ZnO-NPs) grown on indium tin oxide (ITO)-coated glasses were investigated. The room temperature PL showed bright -white -light emission for the undoped ZnO-NPs grown at 600 degrees C, suggesting the close relation between the optical characteristic and "the growth conditions being, carried out for,obtaining the present ZnO-NPs. The reflectivity of the as -grown ZnO-NPs array was about, similar to 29% with the wavelength of the incident light ranging from 200 to 1800 nm. Nevertheless, the reflectance reduced significantly to less than 9.9% when a layer of gold (Au) was deposited on ZnO=NPg by sputtering for 5 min, corresponding to more than 65% reduction in Au -coated ZnQ-NPs (Au/ZnO-NPs). Moreover, the angle -resolved reflectance measurement's on the present Au/ZnO-NPs array show an omnidirectional light -trapping characteristic. These remarkable characteristics, broadband and omnidirectional light -trapping -of Ati/ZnO-NPs, are attributed to the extended effective optical path of the incident light due to subwavelength scattering resulting,from the presence of Au nanoparticics.