We report on studies of sub‐bandgap defect related photoluminescence (DRL) signals originating from radiative recombination through traps in the bandgap of cooled mono‐like silicon wafers. Spectrally resolved photoluminescence (SPL) and multivariate curve resolution (MCR) have been used in combination, to study the behaviour of sub‐bandgap photoluminescence (PL) emissions in wafers cut from different heights in a pilot‐scale mono‐like silicon ingot. No DRL signals were found in the main mono‐like body. Strong defect related sub‐bandgap emissions correlating with heavily dislocated areas, are found directly above some of the seed junctions. The DRL signal exhibits a correlation with the number of axis with small angle misalignment in the junctions of the seeds. The signal conventionally labelled D1 (0.80 eV) decreases with ingot height. A mechanism relating this signal to oxygen is proposed. The signals D3 (0.94 eV) and D4 (1.00 eV) are found to co‐occur, supporting previous studies, and similarly to the D2 (0.87 eV) signal, their strength is found to increase with ingot height. As the content of the transition metal impurities in the ingot is supposed to increase with height, this supports a reported link between the D3 and D4 signals with Fe, as well as a link between D2 and other impurities. An emission previously found in multicrystalline material and labelled D07 (0.70 eV), is found to solely exist as the only DRL signal recorded by us in parasitic crystals, growing into the main mono‐like ingot from the crucible walls. This contradicts the common notion that the D1–D4 signals are strongly related to, and always follow dislocations. Total photoluminescence spectrum (right) and distribution (left) of the PL signal with centre energy 0.70 eV emanating from the parasitic crystals growing into the bulk mono‐like Si crystal from the crucible walls.
In order to improve wafer based silicon solar cell performance with even lower costs, new methods for manufacturing the material are constantly being developed. One approach is to use low cost block casting to make material with primarily monocrystalline character, called mono‐like silicon. Unfortunately, crystal faults readily form and multiply in this structure. These cause the recombination of photogenerated charge carriers lowering the efficiency of solar cells. The socalled D‐line emissions are four luminescence signals (D1–D4) emanating from photoexcited silicon. They are caused by radiative recombination via traps in the band gap and are reported to always occur together in dislocated areas. The behaviour of the D‐line emissions as function of position in a block of mono‐like silicon has been studied by Olsen et al. (article no. http://doi.wiley.com/10.1002/pssa.201700124). The emissions behave differently suggesting they do not have the same origin. A new signal (0.70 eV) is found in areas where the mono‐like character is lost due to formation of material with multicrystalline character. These areas are highly dislocated, however do not exhibit the D1–D4 emissions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.