To apply surface plasmon effects to Si solar cells, thin polymer films containing nanoparticles of silver and gold were fabricated using the spin-coating method. Advantages of this method are that it is simple, and that there is no possibility to produce additional crystal defects as surface recombination centers. Thin polymer films showed an absorption peak, anti-reflection effect and the haze ratio increase. In particular, thin polymer films containing gold nanoparticles were promising for improving Si solar cells, because the film had the longest peak wavelength and the lowest reflectance (3.84% at 800 nm), overall haze ratio increase caused by localized surface plasmon. Enhancement ratio in photocurrent conversion efficiency was 12% for single-crystal Si solar cells after being spin-coated with a thin polymer film containing gold nanoparticles. Enhancement ratio of the external quantum efficiency was 22% at the peak wavelength, caused by antireflection due to scattering by metal nanoparticles.

For current-matching of multi-junction Si solar cells, localized surface plasmons (LSPs) of metal nanoparticles (MNPs) are considered as a new solution because MNPs can reflect or transmit light of specific wavelengths. To predict the LSP effect of MNP films in solar cells, we fabricated gold and silver nanoparticle films by spin-coating onto amorphous Si (a-Si) layer and investigated the optical properties of each film. Gold and silver nanoparticle films have the reflection peaks at 700 nm and 600 nm, respectively. Furthermore, we fabricated films by ink-jet printing to adjust the micro and nano-ordered structure and investigated the correlation between the morphology of the films and the optical properties. MNP films fabricated by ink-jet printing have a more balanced reflection and absorption effect compared to films fabricated by spin-coating. Furthermore, we considered appropriate application in multi-junction solar cells using our measured characteristics of the MNP films.

, 41 (45) 1-11 (2012)