Surface-Plasmon Enhanced Near-Bandgap Light Absorption in Silicon Photovoltaics

One key challenge for silicon-based solar cells is the weak absorption of long-wavelength photons near the bandgap (1.1eV) due to the indirect bandgap of silicon. A large fraction of the AM 1.5 solar spectrum falls into a regime (0.7 μm – 1.1 μm) where silicon does not absorb light well. The capture of these long-wavelength photons imposes a particular problem to the thin-film silicon solar cells. For this reason, thin-film silicon solar cells often incorporate some forms of light trapping mechanisms.