Defect monitoring using scanning photoluminescence spectroscopy in multicrystalline silicon wafers

Abstract

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.

Micrometer-Scale Deep-Level Spectral Photoluminescence From Dislocations in Multicrystalline Silicon

“…Near liquid nitrogen temperature, the D4 peak was reported to be higher than the D3 peak in [7] and [11]. However, the opposite observation was presented in other works [8], [23].…”

“…Some reported spectra in which the D2 line was a less-significant peak embedded on the high-energy side of the intense D1 line [7], [11], [12], [14]. Others reported spectra with the D2 line present, but with D1 absent [9], [13].…”

Luminescence emission from forward- and reverse-biased multicrystalline silicon solar cells

“…36͒ is most likely to be related to thermal donors or oxygen clusters bound to dislocations or trapped in the strain field of dislocations. In a more detailed study, Ostapenko et al 37 reported a very good qualitative correlation of a reduced car- rier lifetime, strong defect photoluminescence at around 0.8 eV, decreased band-to-band photoluminescence, and enhanced dislocation density.…”

Distribution of radiative crystal imperfections through a silicon ingot

“…Recently Mchedlidze associates screw dislocations with a small twist angle to the D-lines and the edge dislocations to non radiative recombination. 13 Investigation of DRL is mainly performed by laboratory-based spectroscopic point mapping methods, such as described by Mudryi et al 14 and Ostapenkoet al 8 Recently single band methods using band pass filters on InGaAs cameras have been reported by Mankovics et al 15 and Schmid et al 16 Also hyperspectral technologies have been applied by Peloso et al, 17 as well as by Olsen&Flo 18 and Burud et al 19 The advantage of using hyperspectral imaging is that the entire spectrum is acquired at each point. Instead of selecting a priori regions for detailed studies with e.g.…”