Broadband enhancement of optical absorption in a silicon nanowire flexible thin film

A silicon nanowire (SiNW) array was embedded into a polydimethylsiloxane matrix to fabricate a flexible thin film solar cell in which a rugged metallic back surface was formed at the bottom. Superior light scattering of the randomly arrayed SiNWs significantly improved the light absorptance in a short wavelength region (λ < 700 nm). The rugged morphology of metallic back surface excited the surface plasmon polaritons (SPPs) along the interface between the metal and Si, which showed a plasmonic potential to enhance light absorption in a long wavelength region (λ > 700 nm). This feature was attributed to the three major routes for light trapping: back reflection, SPP resonance, and SPP scattering. This nanowire thin film showing the rugged back surface yielded the light absorption of ~ 92.6% using only ~ 5% of silicon required for conventional crystalline solar cells.