Trapping light with nano-scale silicon spheres

A new approach to trapping light using nanometre thick layers of silicon shells is presented in Nature Communications this week. The findings provide a method of enhancing the absorption properties of devices like solar cells using ultrathin coatings. To achieve the best performance from optical devices, control of their absorption properties is crucial. Many schemes exist to achieve this, such as specially structured layers applied to the surface, although they often suffer from being expensive or too thick to be practical for applications. Yi Cui and co-workers developed a new type of absorbing structure using layers of spherical silicon nanoshells. The sub-wavelength size of the shells, combined with their spherical shape, produced resonances that confine and guide the light in the shells, enhancing the absorption compared to equivalent flat samples. Single layers of shells of 50 nanometre thickness showed similar properties to micron-thick films of silicon, enabling a faster production time using less material. The flexibility and simplicity of these structures may provide gains in light management for various optical devices, from solar cells to photodetectors.