Roughness-induced enhancement of optical absorption in random media

The effect of surface roughness on the optical absorption of a porous material is numerically investigated. We performed a comparative study among different porous geometries and we demonstrate that the presence of the roughness significantly increases the optical absorption of light. This effect is optimized by using a proper matching layer that minimizes losses and maximizes absorption. Enhanced absorption is achieved over a broad range of wavelengths in these simple bilayered structures. The results of this work can be used to design more effective light trapping devices, e.g., third-generation photovoltaic backreflector exploiting the bandgap incident radiation.