Light trapping in the absorber layer of thin-film solar cells is of great importance for obtaining a high photocurrent. A novel light-trapping technique is based on light scattering by metal nanoparticles through excitation of localized surface plasmons. By evaporation of thin silver layers of different thicknesses followed by thermal annealing, silver nanoparticles with different sizes were formed. We show that the plasmon resonance wavelength can be tuned by changing the embedding medium and the particle size. Furthermore, amorphous silicon solar cells with silver nanoparticles embedded between the absorber layer and the back reflector were fabricated. The effect of different sizes of the particles on the solar cell performance was studied. The performance of the solar cells was characterized by quantum efficiency and current-voltage measurements. Both the external quantum efficiency in the wavelength region of 600 to 800 nm and the current density increase as particle size increases, but remain lower than those of the reference device without particles. These results demonstrate that nanoparticles can enhance light trapping, provided that parasitic absorption in the nanoparticles is minimized. This can be achieved by better control of particle shape and size using improved fabrication techniques.@en

The application of a light trapping technique based on light scattering by metal nanoparticles through excitation of localized surface plasmons was studied. Our objective was to investigate experimentally the most suitable location for the metal nanoparticles inside hydrogenated amorphous silicon (a-Si:H) solar cells for efficient light scattering. Silver nanoparticles were embedded either at the front, inside, or at the rear of the a-Si:H absorber layer. Embedding the nanoparticles at the back of the absorber layer turned out to be most promising. We found that when the size of the particles was increased, the external quantum efficiency increased for wavelengths longer 600 nm. This was caused by increased light scattering and reduced parasitic absorption for the larger particles. Nonetheless, it proved challenging to enhance the performance of a-Si:H solar cells by embedding silver nanoparticles when state-of-the-art light trapping techniques are already applied.@en

Photon management is one of the key issues for improving the performance of thin-film silicon solar cells. An important part of the photon management is light trapping that helps to confine photons inside the thin absorber layers. At present light trapping is accomplished by the employment of the refractive-index matching layers at the front side and the high-reflective layers at the back contact of the solar cells and scattering of light at randomly surface-textured interfaces. In this article key issues and potential of light management in thin-film silicon solar cells are addressed. Novel approaches for light trapping are presented such as i) surface textures based on periodic diffraction gratings and modulated surface morphologies for enhanced scattering and anti-reflection, ii) metal nano-particles introducing plasmonic scattering, and iii) one-dimensional photonic-crystal-like structures for back reflectors.@en

A novel light trapping technique for solar cells is based on light scattering by metal nanoparticles through excitation of localized surface plasmons. We investigated the effect of metal nanoparticles embedded inside the absorber layer of amorphous silicon solar cells on the cell performance. The position of the particles inside the absorber layer was varied. Transmission electron microscopy images of the cell devices showed well defined silver nanoparticles, indicating that they survive the embedding procedure. The optical absorption of samples where the silver nanoparticles were embedded in thin amorphous silicon layer showed an enhancement peak around the plasmon resonance of 800 nm. The embedded particles significantly reduce the performance of the fabricated devices. We attribute this to the recombination of photogenerated charge carriers in the absorber layer induced by the presence of the silver nanoparticles. Finally we demonstrate that the fabricated solar cells exhibit tandem-like behavior where the silver nanoparticles separate the absorber layer into a top and bottom part.@en