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Requirements for efficient hole extraction in transition metal oxide-based silicon heterojunction solar cells

: Meßmer, Christoph Alexander; Bivour, Martin; Schön, Jonas; Hermle, Martin

Postprint urn:nbn:de:0011-n-5069542 (3.1 MByte PDF)
MD5 Fingerprint: 796c949ae8415a1c680d923c8c5171d8
Erstellt am: 30.8.2018

Journal of applied physics 124 (2018), Nr.8, Art. 085702, 23 S.
ISSN: 0021-8979
ISSN: 1089-7550
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
Bundesministerium für Wirtschaft und Technologie BMWi
0324141; SELEKTIV
Selektive Kontaktsysteme für hocheffiziente Siliziumsolarzellen; Teilvorhaben: Prozesse und Solarzellen
Zeitschriftenaufsatz, Elektronische Publikation
Fraunhofer ISE ()
fundamental; heterojunction; inversion layer; simulation; TMO; Photovoltaik; Silicium-Photovoltaik; Herstellung und Analyse von hocheffizienten Solarzellen; layer

Transition metal oxides (TMOs) are of increasing importance for many applications reaching from thin-film transistors and non-volatile memory to novel contact layers in photovoltaics. Due to their tunable electrical properties and high transparency, TMOs are also promising candidates as contact layers in silicon heterojunction solar cells already leading to cell efficiencies of about 22%. However, the current extraction of charge carriers via these thin contact layers is still not fully understood. To assist the engineering of novel silicon heterojunctions, numerical device simulations are used to improve knowledge regarding relevant heterojunction and thin film properties. The efficient current extraction from a silicon absorber is investigated with Sentaurus TCAD for a TMO-based hole contact. It is shown that for an ideal hole extraction from the induced crystalline silicon pn-junction via the amorphous silicon buffer and the TMO into the external metal electrode, two requirements have to be fulfilled: A) A sufficiently high TMO work function is needed to ensure a high hole conductivity (via a high charge carrier ratio p/n) in the induced pn-junction within the silicon absorber.B) Extraction of those holes into the TMO calls for efficient trap-assisted tunneling. Experimental evidence for a limitation of hole extraction by A) and B) is given for a variety of TMO based hole contacts using molybdenum oxide.