Advanced Characterization of Defects in Silicon Wafers and Solar Cells

Understanding the recombination properties of bulk defects in silicon wafers is essential for further improvement of performance and stability of silicon solar cells. This thesis focuses on the characterization of the electrical properties of bulk defects in silicon. Injection dependent lifetime spectroscopy, a technique characterizes defects from the measured charge carrier lifetime, is the main technique investigated and ameliorated in this thesis. However, other techniques are also applied together with injection dependent lifetime spectroscopy for a more reliable defect characterization. The thesis first presents an injection dependent lifetime measurement system. This system allows measurement of charge carrier lifetime with a wide injection range and temperature range. The charge carrier lifetime can be measured using both photoconductance and photoluminescence detectors. The methodology of injection dependent lifetime spectroscopy analysis is then investigated. A new approach of defect parameterization is proposed. In this new approach, the equation correlating injection dependent lifetime and defect parameters is inversely solved using the Newton-Raphson method. Apart from this new approach, this thesis expands injection dependent lifetime spectroscopy from single-level defects to two-level defects. The developed methods are then applied to investigate the newly discovered recombination active defects in float-zone silicon. Injection dependent lifetime spectroscopy together with deep-level transient spectroscopy are applied to extract the recombination parameters of these defects. A combination of these two techniques is demonstrated to be very beneficial for accurate defect parameterization. Apart from recombination active defects, trap-like defects are also investigated in this thesis. Although traps might be less harmful for the performance of solar cells, they can cause artefacts to photoconductance based injection dependent lifetime measurements and impede accurate lifetime spectroscopy analysis. The properties of both minority carrier traps and majority carrier traps in n-type Czochralski are investigated using photoconductance measurements. At the end of this thesis, a new approach of photoluminescence imaging using non-uniform illumination is developed in order to achieve accurate quantitative charge carrier lifetime image for non-uniform samples. This approach can potentially be combined with injection dependent lifetime spectroscopy for a spatially resolved characterization of non-uniformly distributed defects in silicon wafers or solar cells.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2020

Author dc:creator

• Zhu, Yan

• Solar cells
• Defects
• Silicon wafers

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/21648

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/64988