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Structures of intragrain defects were investigated by photoluminescence (PL) mapping tomography in multicrystalline silicon wafers for solar cells. PL dark patterns were observed in short minority carrier diffusion length regions, and we confirmed that the patterns came from the intragrain defects. The tomography revealed that the defects have planelike structures extended to the crystal growth direction. We also found that the growth conditions affect the structures of the defects: slower solidification leads to larger defects with lower density. Origins of the defects were analyzed by low-temperature PL spectroscopy, electron backscatter diffraction pattern measurement and etch-pit observation. We concluded that the defects are metal contaminated dislocation clusters which originate from small-angle grain boundaries.

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Al-doped ZnO (AZO) films were deposited onto glass substrates by RF magnetron sputtering for solar cell applications. The effects of the Al 2 O 3 doping concentration on the structural, electrical, and optical properties of the AZO films were investigated. As the Al 2 O 3 doping concentration was increased to 4.0 wt %, X-ray diffraction (XRD) showed a deterioration in the (002) peak intensity and a shift towards a higher angle. The best electrical properties ( ¼ 9:8 Â 10 À4 cm, H ¼ 22 cm 2 V À1 s À1 , and n e ¼ 2:89 Â 10 20 cm À3 ) were obtained in the AZO sample containing 2 wt % Al 2 O 3 . Optical transmission >83% in the visible range was also observed and the optical bandgap was increased to 3.63 eV at an Al 2 O 3 concentration of 4 wt %. For photoluminescence (PL) spectra, one UV emission peak at approximately 3.2 eV and a broad peak in the visible range from 2.3 to 2.7 eV were observed at Al 2 O 3 doping concentrations ranging from 0 -2.0 wt %. Blue emission at 2.67 eV, which indicates a non-stoichiometric structure, was only observed in the 4 wt % doped AZO films.

The present article focuses on the effect of annealing temperatures about the Sn induced crystallisation of hydrogenated amorphous Si (a-Si:H) thin films, which are used to fabricate polycrystalline Si (poly-Si) film. The a-Si:H thin films are coated onto Sn metal thin film and subsequently annealed from various temperatures. These are crystallised by annealing for 1 h at 300°C and identified by XRD spectroscopy for the investigation of each phase. Process temperature for crystallisation should not be high because a eutectic temperature of Si–Sn is ∼232°C. Si crystal patterns of the prepared samples showed the tendency of changing from (111) to (002) with increasing temperature. It indicates that the crystal phases depend strongly on the annealing temperature of Sn induced a-Si:H thin films for the preparation of poly-Si film. Semiconducting type of Sn induced poly-Si films were shown in n-type through Hall effect measurement.