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Samples containing silicon nanowires (Si-NWs) and highly porous structures (P-Si) were prepared by electroless wet chemical etching (EWCE) of crystalline silicon wafers using various etching parameters. Photoluminescence (PL) measurements were performed with excitation at 488 nm and a photon energy flux of 337mWcm (2). According to the diameters of the Si-NWs (> 10 nm), from quantum confinement (QC) theory no shift in PL peak energy compared to the bandgap of crystalline silicon is expected. However, PL measurements show peak emission energies ranging between 1.4 and 1.6 eV. After further treatment of the samples with HF, substantial PL emission was still detectable with the measured PL peak pinned at 1.4 eV irrespective of etching time. We explain the observations by the hypothesis that the persistent part of PL emission is generated by nanocrystals located at the rough sidewalls of the Si-NWs or residing within the porous sample structure. The part of the PL, which was present before HF treatment, but vanished after the treatment, is attributed to the presence of silicon suboxide surrounding the Si-NWs or covering other Si surfaces. This hypothesis is explored by means of three sample series, prepared with different preparation parameters. In the first series the time used during the initial metallization step in order to prepare an Ag nanoparticle layer on the top surface was varied, in the second series the etching time was the changed parameter and in the third series the HF to H(2)O(2) concentration ratio was varied. [GRAPHICS] Strong visible orange colored PL of a sample produced by EWCE starting from a heavily doped wafer (n-type c-Si (111), As as dopant) and excited at 337 nm ( the sample was mounted on a glass substrate. Blue luminescence is due to the substrate). (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

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One method for producing CuInSe 2 (CISe) absorber layers is electrodeposition followed by annealing. Replacing the commonly used furnace annealing step with a laser can reduce annealing times by 2-3 orders of magnitude: from 30 minutes to 1 s. However, laser processing has, to date, not resulted in absorber layers which can form functioning final devices. One reason is due to Se loss during annealing even on these short timescales. We show how this Se loss is reduced by using a background partial pressure of Se (P Se ) during annealing. Higher P Se results in increased grain size and drastically increased photoluminescence yield. The introduction of an elevated P Se in the laser annealing chamber enabled the fabrication of the first known CuInSe 2 photovoltaic device using electrodeposition followed by laser annealing which gave 1.6% efficiency.

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