Short wavelength absorption loss due to plasmonic nanoparticles top-coated on thin film solar cells

Nanoplasmonic metal structures in the front end of thin film solar cells are able to enhance light absorption in the band gap region but result in absorption losses at short wavelengths. The particles are designed to resonate near the bandgap (long wavelengths) of the semiconductor, hence they appear electrically large at short wavelengths. Due to their apparently large size, they begin to shadow the semiconductor absorber layer. The shadow effect depends not just on electrical size but also the geometry of the metal nanoparticle. The geometry dependence of light absorption at short wavelengths for a top-coated thin film solar cell is studied in this paper by comparing the short wavelength absorption in thin film solar cells top-coated with metal nanospheres and nanohemispheres. The light absorption at short wavelengths is lower than that of the same model without any nanoparticle coating. Light incident on the metal structures experiences very weak forward scattering at short wavelengths and more light is reflected back into the air.