Solar Cells with Passivating Contacts − Investigation of Their Temperature- and Illumination-Dependent Performance and Surface Passivation

Although photovoltaic (PV)-based electricity has become the cheapest form of electricity production, further reduction in the PV cost is still required to realise the full potential of this technology. This can be achieved by improving solar cell efficiency. For this purpose, silicon (Si) solar cells with passivating contacts have been developed to eliminate the recombination at the Si/metal interface which significantly impacts the cell performance due to the extremely high surface recombination velocity. Up to now, the characterisation of the performance of solar cells with passivating contacts has been typically conducted at standard testing conditions. However, it does not reflect the cell performance at actual operating conditions encountered in the field which significantly deviate from the standard conditions. Therefore, knowledge regarding the performance of these cells under realistic operating conditions is a considerable need. In this thesis, the temperature- and illumination-dependent performance of solar cells using passivating contacts such as tunnel oxide passivated contact (TOPCon), Si heterojunction (SHJ), and transition metal oxide (TMO)-integrated solar cells is investigated. Temperature coefficients (TCs) of the electrical properties of these solar cells are extracted and compared to those of the common cell structures in the field. To gain a deeper understanding of the cells’ TCs, the temperature-dependent behaviour of the corresponding passivating contacts is examined. The findings from this thesis are of great importance for the evaluation and optimisation of the performance of solar cells using passivating contacts in actual operating conditions. They also highlight the advantages of using this cell technology in the field. In solar cells with passivating contacts, the surface passivation is typically good quality and the impact of bulk recombination on further improvement of the cell efficiency becomes significant. The use of high-resistivity wafers may offer a great opportunity to significantly reduce the Auger recombination and hence, to further improve the performance of these solar cells. In this thesis, the possibility of using such wafers for solar cells using passivating contacts is assessed. The findings demonstrate that there is no limitation in using high-resistivity wafers for SHJ solar cells under field operating conditions. The possibility of using high-resistivity wafers for SHJ solar cells may be potentially valid for TOPCon and TMO-integrated solar cells. Although the recombination at the Si interface has been significantly reduced using passivating contacts, the type of covering metal (or degenerated doped transparent conductive oxide) electrodes can possibly impact the recombination statistic at the Si/passivating contact interface via their work function. In this thesis, the impact of the metal work function on surface passivation is studied. Guidance on the selection of suitable metals to minimise contact recombination is proposed. The findings present an additional potential pathway for further improving the performance of solar cells using passivating contacts, especially TMO-based passivating contacts with typical ultra-thin layers. A deeper understanding of the surface carrier-dependent recombination in devices using passivating contacts is critically important for a further improvement of the surface passivation quality and carrier selectivity. This thesis investigates the carrier-dependent recombination at the Si surface using a novel method. An advanced model is established to extract key interfacial parameters. The unique information gained from this investigation helps to realise the full potential of this method for the investigation of surface recombination statistics in the field.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2023

Author dc:creator

• LE, Huy Tuan Anh ; https://orcid.org/0000-0002-9395-0771

• Temperature dependence
• Illumination dependence
• Temperature coefficient
• Passivating contacts
• Silicon solar cells
• Polysilicon
• TOPCon
• MonoPoly™
• POLO
• SHJ
• TMO
• MoOx
• TiOx
• High-resistivity wafers
• Surface recombination
• Quasi-steady-state photoluminescence
• Saturation current density
• Work function
• Capture cross-section

Statement dc:rights

• open access
• CC BY 4.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/25334

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/101627