On the method of photoluminescence spectral intensity ratio imaging of silicon bricks: Advances and limitations

Abstract

Spectral photoluminescence imaging is able to provide quantitative bulk lifetime and doping images if applied on silicon bricks or thick silicon wafers. A comprehensive study of this new method addresses previously reported artefacts in low lifetime regions and provides a more complete understanding of the technique. Spectrally resolved photoluminescence measurements show that luminescence originating from sub band gap defects does not cause those artefacts. Rather, we find that optical light spreading within the silicon CCD is responsible for most of the distortion in image contrast and introduce a method to measure and remove this spreading via image deconvolution. Alternatively, image blur can be reduced systematically by using an InGaAs camera. Results of modelling this alternative camera type and experiments are shown and discussed in comparison. In addition to eliminating the blur effects, we find a superior accuracy for lifetimes above 100 ls with significantly shorter, but dark noise limited exposure times. V

Mechanically stacked 4-terminal III-V/Si tandem solar cells

“…cracks) [14][15][16][17] • Prediction of electrical properties e.g. localized series resistance and saturation current [11,18,19] Programs incorporating these features can be also used to evaluate the state/quality of the PV device. Only few programs have their own graphical user interface (GUI) [15] and are commercially available [16,19,20].…”

Imaging As-Grown Interstitial Iron Concentration on Boron-Doped Silicon Bricks via Spectral Photoluminescence

“…However, it can only provide a lower than 20% relative uncertainty on bulk lifetime, if spreading of light in the detection device can be either prohibited or compensated for. The light spreading was found to significantly deteriorate the analysis [32]. Hence, using either an appropriate direct semiconductor detector (e.g., In-Ga-As) or applying a deconvolution process is critical.…”

“…3). The spectral PLIR method has been described previously in [31] and [32]. It utilizes the bulk lifetime-dependent shift in spectral PL emission to quantify the silicon minority carrier bulk lifetime.…”

“…This paper extends the use of PL imaging from the measurement of the interstitial iron concentration on passivated silicon wafers [25], [30] to measuring directly on the unpassivated brick surface. We demonstrate the measurement of bulk lifetimes on unpassivated surfaces before and after iron-boron (Fe-B) pair dissociation using the spectral photoluminescence intensity ratio (PLIR) analysis [31], [32]. Experimental work is performed on directionally solidified boron-doped silicon bricks, as it is the most widely used type of ingot crystallization in the photovoltaic industry [33].…”

Synchrotron-based analysis of chromium distributions in multicrystalline silicon for solar cells

“…Area 3 (red circles) contains high dislocation density regions with higher lifetime and [Cr i ] after the EXT process. Our PL setup does not include corrections for lateral carrier diffusion due to inhomogeneous excess carrier densities, 23,29 photon scattering or reabsorption within the sample, 30 or photon spreading within the sensor, 31,32 all of which may impact the spatial The results in each area can be explained by considering that the higher temperature EXT process may more effectively dissolve small Cr-rich precipitates. In areas of low dislocation density (Area 1), Cr i atoms may be "frozen" into bulk intragranular regions during cooling.…”