Self Assembled Monolayers for Passivated Contacts

Bill Nemeth, Steve Harvey, Matt Young, Matt Page, San Theingi, Ryan France, Caroline Lima Souza de Salles, Matt Hartenstein, Kejun Chen, Vincenzo LaSalvia, Markus Kaupa, Abigail Meyer, David Young, Pauls Stradins

Research output: NRELPresentation


Passivated contacts mitigate defects typically encountered due metallization of solar cells. We deposit amorphous silicon (a-Si:H) on an oxidized silicon wafer via PECVD and anneal at high temperature to crystallize into polysilicon passivated contact. One drawback is the absorption of the polysilicon between grid fingers, so removal of this material is desirable to maximize Jsc. Alternatively, interdigitated back contact cells rely on a gap between n- and p- fingers, which is commonly etched to ensure electronic isolation. We utilize a self assembled monolayer (SAM) using hexamethyldisilazane (HMDS) as a precursor to pattern and etch amorphous silicon (a-Si:H) and polysilicon without the need for photoresist. Ultraviolet light exposure oxidizes the HMDS by photocleaving the organic groups [1] of the SAM leaving a patterned SiO2. Directly soaking this in TMAH will eventually etch the SAM and the silicon, where the SiO2 serves as an etch mask. Inversely, a dilute HF dip selectively etches this SiO2 and the SAM remains. A subsequent soak in TMAH selectively etches the underlying silicon, where the SAM serves as an etch mask. Importantly, we find that the SAM can remain intact for metallization, where we measure 10 mO-cm2 specific contact resistivity on n-type polysilicon.
Original languageAmerican English
Number of pages16
StatePublished - 2021

Publication series

NamePresented at the 31st International Photovoltaic Science and Engineering Conference (PVSEC-31), 13-15 December 2021

NREL Publication Number

  • NREL/PR-5900-81309


  • passivation
  • silicon


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