A team from Nanyang Technological University, Singapore, has conducted a detailed study, which employs a full wave finite element method and hexagonally arranged Si nanopillar/wire arrays. The aim is to clearly describe the interaction process between incident light and nano-structures, and to clarify the primary mechanism responsible for the enhancement in light absorption.

The scientists found that the wave-guided modes formed at some designated wavelengths do increase light trapping to some extent at the base of the scattering-based absorption enhancement region, but do not affect the change trend of light trapping capability with the Si nanopillar length.

Furthermore, the team compared the light absorption behaviors of Si nanopillar arrays with different arrangement schemes, and found that there is little impact of the array symmetry on the light trapping capability.

The researchers point out that for the Si nanowire test samples prepared using both bottom up and top down paradigms, the microstructures are not as uniform as the features used for modelling, which will affect the formation of waveguide modes. As a result, scattering-induced light absorption enhancement is likely to become the main consideration when fabricating devices.

Further details can be found in the journal Nanotechnology.