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In conjunction with the two-level model the temperature behaviour of the dislocation-related D1-peak follows the T-behaviour of the band gap. Based on luminescence observations in our laboratory and on literature data we propose a ∼30 meV wide domain of the D1 peak. Altogether, the D1-peak position ranges between about 0.76 eV at 300 K and nearly 0.84 eV at a few K. It was shown that the energetic shift for a certain temperature is caused by external electric fields, by excitation level, that affects the intrinsic dislocation field, and by elastic stress. The luminescence of oxygen-related defects / precipitates might be described by a line at ∼ 0.77 eV (P-line) that does not depend on temperature. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on a method for fast detection of defect rich areas in multicrystalline silicon solar wafers. It is based on photoluminescence imaging of the whole wafers and detects both the band-to-band radiation as well as the dislocation specific radiation D1. To illustrate the capabilities of the method we examined 5.0 × 5.0 cm2 wafer pieces in different stages of their processing. The achieved resolution of the D1 images was ∼120 μm, within a total recording time of 550 ms.

We studied the correlation between the appearance of defects and of breakdowns in fully processed solar cells by electroluminescence imaging. Images under forward and reverse bias were recorded, revealing defective areas and breakdown sites of the cells, respectively. In the experiments presented here an InGaAs camera system was used, which allows us to detect short wave infrared light in the 900–1700 nm range. Applying a forward bias the band-to-band luminescence (1.1 eV/1150 nm) and the defect-related luminescence (0.8 eV/1550 nm) were imaged. Both imaging techniques reveal mainly dislocation-rich areas and grain boundaries. Applying a reverse bias (approximately −10 V), breakdown luminescence occurs. It was found that the distribution of the breakdown sites across the solar cells is different from the distribution of the defects showing luminescence at 0.8 eV (grain boundaries, dislocations). The spatial separation between those defects and the breakdown sites was clearly evidenced by high resolution imaging. Possible reasons for such spatial separation are discussed.

Here we report on two different approaches, which allow rapid photoluminescence imaging of dislocation-related D1, and band-to-band radiation on multicrystalline solar cell wafers at room temperature. We compared a new light emitting diode based method with the recently introduced pulsed laser based method. With both techniques we obtained spatially resolved images from 15.6 × 15.6 cm2 wafers originating from different stages of the standard solar cell production process, showing that these techniques are highly interesting for inline quality control. Both methods provide homogeneous illumination over the whole sample area. With a resolution around 300 μm, and a total recording time of ∼45 s, full D1 images could be captured by the new diode technique. The most promising fact was that surface artifacts did not lead to any noticeable disturbance in the D1 image. For acid textured wafers, the pulsed laser based method was clearly in advantage over the continuous diode technique. Possible explanations are discussed in the text. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Here we report on a novel method, which allows rapid photoluminescence imaging of band-to-band and dislocation-related radiation, D1, on multicrystalline silicon wafers at room temperature. We demonstrate spatially resolved 5.0 × 5.0 cm2 D1-images, with a resolution of ∼120 µm, within a total recording time of 550 ms. The method provides homogeneous illumination over the whole sample area. Comparison with results from a conventional photoluminescence mapping technique demonstrates the potential of this new method for application as an in-line wafer characterization technique.