Complex photonic structures for energy efficiency

Abstract

Summary. -Photonic structures are playing an increasingly important role in energy efficiency. In particular, they can help to control the flow of light and improve the optical properties of photovoltaic solar cells. We will explain the physics of light transport in such structures with a special focus on disordered materials.

Optical Properties of Nanoporous Germanium Thin Films

“…This signal enhancement must be related to two different effects: light trapping within the pores and carrier confinement. The first effect causes absorption enhancement, which has already been reported for a two-dimensional random film of finite thickness, ,, but never reported until now for 3D systems. The second effect has already been observed in ordered germanium nanoporous materials, and in Ge nanowires, but never in nanoporous Ge films obtained by ion implantation.…”

“…Interference could lead to weak or strong (Anderson) localization, where diffusion is decreased or completely halted. It has been demonstrated that a two-dimensional random film of finite thickness can lead to a large broad-band absorption enhancement, but no direct observation of this phenomena in a three-dimensional system has been reported until now. , …”

“…It has been demonstrated that a twodimensional random film of finite thickness can lead to a large broad-band absorption enhancement, 2 but no direct observation of this phenomena in a three-dimensional system has been reported until now. 5,6 Efficient solar cell conversion can be achieved if optical absorption and photogenerated charge-carrier transport are both optimized. The first issue is obtained if optimum matching between the solar spectrum and absorption edge is achieved, that is, if a material with tunable energy gap is employed for the cell.…”