Development and application of the scanning Kelvin probe for solar cell defect analysis.

The Kelvin probe is a non-contact, non invasive capacitor device capable of detecting changes in local work function and surface state and has become a valuable tool for surface science research. This thesis presents three years of work centred on the development and novel applications of the scanning Kelvin probe (SKP) technique. Initially the capacitive interaction between the Kelvin probe and the sample under analysis was investigated. The limitations of the Kelvin probe as a technique are discussed; specifically the effect stray flux emanating from the sides of the probe tip has on final image quality. A mathematical model to simulate the interaction between the Kelvin probe tip and the sample under analysis was successfully developed and then extended to include the sides of the Kelvin probe. This expanded model was successfully used to simulate the contribution of the tip sides to the total capacitance of the Kelvin circuit, how this contribution changed as the tip dimensions were reduced and further more the simulation showed that the additional capacitance originating from the tip sides actively degrades the resolution of SKP scans. The model's predictions were confirmed with experimental measurements using specially designed tips which allow their dimensions to be changed before introducing a novel "actively shielded" upsilon-tip (200 upsilon m) designed to nullify the effect of the tip sides. Details of the manufacturing process for this new tip are discussed and the tip performance is evaluated. The Kelvin probe technique was successfully able to detect, image and then re-image point charge defects in or on top of the Si3Ni4 passivation layer on a mc-Si (Multicrystalline silicon) solar cell. Furthermore a high resolution SKP has successfully produced images showing direct evidence of polytype related surface potential variations caused by the surface orientations of mc-Si. The Kelvin probe was demonstrated to be capable of distinguishing between bulk silicon of the solar cell and high trapping density silicon commonly found at cell edges. Idle Kelvin probe was also successfully used for the analysis of solar cell surface preparation treatments by measuring the magnitude, polarity and decay time of the stored charge making it an ideal tool for the analysis of novel passivation coatings.

Grantor dc:publisher.institution

Robert Gordon University

Year dc:date.issued

2006

Author dc:creator

• Forsyth, Gregor

Advisor dc:contributor.advisor

• I. Baikie

• Kelvin probe
• Surface state
• Work function
• Surface science
• Stray flux emination
• 200 upsilon m
• Si3Ni4 passivation layer
• Multicrystalline silicon
• Solar cells

Language dc:language

en

Identifier

oai:rgu-repository.worktribe.com:2807385
https://doi.org/10.48526/rgu-wt-2807385

OAI identifier oai:identifier

oai:rgu-repository.worktribe.com:2807385