Scanning photoluminescence (PL) spectroscopy was performed on as-grown and processed multicrystalline silicon (mc-Si) wafers to investigate the defect distribution affecting the efficiency of solar cells. In highly inhomogeneous mc-Si prepared by (i) edge-defined film-fed growth or (ii) a block-casting technique, regions of a wafer with enhanced recombination activity and reduced minority carrier lifetime exhibit an intensive 'defect' PL band at room temperature with the maximum at about 0.8 eV. By comparing PL mapping with the distribution of dislocations, we present experimental evidence that the 0.8 eV band corresponds to electrically active dislocation networks. This was confirmed using low-temperature PL spectroscopy, which revealed a characteristic quartet of the dislocation D-lines. One of these dislocation lines, D1, can be tracked as temperature increases and linked to the 'defect' band. Strong linear polarization of the 0.8 eV PL band corresponds to a preferential localization of defects in regions with a high level of elastic stress measured with scanning infrared polariscopy. The origin of the 0.8 eV PL band is attributed to dislocations contaminated with impurity precipitates.

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Photoluminescence (PL) mapping was performed on polycrystalline silicon wafers at room temperature. Two PL bands are observed: (1) a band-to-band emission with a maximum at 1.09 eV, and (2) a deep “defect” luminescence at about 0.8 eV. PL mapping of 10 cm×10 cm wafers revealed inhomogeneity of the band-to-band PL intensity which could be correlated to the distribution of minority carrier diffusion length in the wafer bulk. We have also observed that the intensity of the 0.8 eV band is strongest along those grain boundaries where the band-to-band PL is suppressed as well as minority carrier diffusion length. The origin of the 0.8 eV luminescence band is discussed.

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We performed non-contact and non-destructive spatially resolved characterization of traps and recombination centres in two-inch-diameter p-type 4H-SiC wafers using thermally stimulated luminescence (TSL) and scanning room temperature photoluminescence (PL). The TSL glow-curve maximum is located at about 190 K for the Al-doped wafers and the TSL spectrum has a maximum at 1.8 eV, which coincides with the spectrum of the 'red' PL band in the same crystal. The TSL intensity exhibits a noticeable inhomogeneity across the wafers. The spatial distribution shows a negative contrast compared to PL maps, indicating a variation of concentration of the TSL centres across the wafer. The origin of the centres is discussed.