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We present an experimental study on the influence of annealing temperature on morphological changes of colloidal silver nanoparticles (Ag NPs) and their optical response. Monodisperse colloidal Ag NPs with diameter of 164 nm ± 15 nm have been fabricated by a facile two-step synthesis approach. The annealing effects on the Ag NPs have been investigated by means of optical measurements, scanning electron microscopy, x-ray photoelectron spectroscopy and x-ray diffraction. By annealing up to 440 °C morphology and chemical compositions of the Ag NPs changed. These changes affect the particle size and distribution, surface morphology, crystallinity and, most importantly, the oxidation state of the surface layer. The removal of an oxide layer leads to stronger light scattering from the nanoparticles and decreases parasitic light absorption at wavelengths above 400 nm. Strong light trapping has been observed for a silicon thin film with embedded annealed Ag NPs. This study demonstrates that colloidal Ag NPs for plasmonic solar cells need to be carefully processed and that they can potentially achieve high scatter efficiencies.

This work reports the spectral characterisation of CuInS 2 (CIS) layers for solar cell devices by Raman scattering. The Raman spectrum from CIS is characterised by a dominant A 1 mode at approximately 290 cm −1 , being the position and width of the mode sensitive to the CIS structural quality. Besides, layers with poor structural quality show the appearance in the spectra of an additional line, not allowed for chalcopyrite crystals, at approximately 305 cm −1 . The relative intensity of this line has been proposed as a further marker for film quality. To deepen in the knowledge of the origin of this mode, Raman scattering measurements are performed in both polycrystalline and epitaxial layers under different conditions, including resonant Raman and different polarisation configurations. The origin of the mode is discussed in terms of (i) the presence of phases with different symmetry as Cu-Au ordering, and (ii) the possible existence of defect-related local vibrational modes.