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Integrating transparent conductive oxides to improve the infrared response of silicon solar cells with passivating rear contacts

: Tutsch, Leonard; Feldmann, Frank; Bivour, Martin; Wolke, Winfried; Hermle, Martin; Rentsch, Jochen

Postprint urn:nbn:de:0011-n-5153183 (350 KByte PDF)
MD5 Fingerprint: 7a750b2348b3bf2ce1d9720603aed819
Copyright AIP
Erstellt am: 23.10.2018

Ballif, C. ; American Institute of Physics -AIP-, New York:
SiliconPV 2018, 8th International Conference on Crystalline Silicon Photovoltaics : 19-21 March 2018, Lausanne, Switzerland
Woodbury, N.Y.: AIP, 2018 (AIP Conference Proceedings 1999)
ISBN: 978-0-7354-1715-1
Art. 040023, 6 S.
International Conference on Crystalline Silicon Photovoltaics (SiliconPV) <8, 2018, Lausanne>
European Commission EC
H2020-Low-cost, low-carbon energy supply - Developing the next generation technologies of renewable electricity and heating/cooling; 727529; DISC
Double side contacted cells with innovative carrier-selective contacts
Konferenzbeitrag, Elektronische Publikation
Fraunhofer ISE ()

This work addresses the development of a transparent conductive oxide (TCO)/metal stack for n-type Si solar cells featuring a tunnel oxide passivating rear contact (TOPCon). While poly-Si based passivating contacts contacted by local fire-through metallization currently show an increased recombination at the metal contacts and a poor infrared (IR) response, we aim to realize a full-area metallization which maintains the high level of surface passivation and avoids IR losses. Some research groups have reported that sputtering TCOs on poly-Si based passivating contacts degrades the surface passivation and unlike the SHJ cells this degradation cannot be cured completely at Tcure ∼ 200°C. However, the higher thermal stability of TOPCon allows for higher Tcure of up to 400°C, which can effectively restore the surface passivation. On the other hand, the contact resistivity (ρc) of the TOPCon/ITO/metal contact increased by several orders of magnitude in our test structures during annealing at such high temperatures. Possible reasons like the formation of an interfacial oxide are currently under investigation. Increasing the poly-Si thickness and/or doping mitigated the effect of sputter damage, but this will come at the cost of more parasitic absorption. However, by adapting the sputter and the subsequent annealing process, we were able to realize low damage deposition of ITO (loss in implied Voc ∼ 7 mV) on thin, lowly doped poly-Si layers on textured wafers, yielding reasonable contact properties (ρc ∼ 40 mΩcm2; of the whole rear contact stack).