In Situ Plasma‐Grown Silicon‐Oxide for Polysilicon Passivating Contacts

Abstract

Large‐scale manufacturing of polysilicon‐based passivating contacts for high‐efficiency crystalline silicon (c‐Si) solar cells demands simple fabrication of thermally stable SiOx films with well controlled microstructure and nanoscale thickness to enable quantum‐mechanical tunneling. Here, plasma‐dissociated CO2 is investigated to grow in situ thin (<2 nm) SiOx films on c‐Si wafers as tunnel‐oxides for plasma‐deposited, hole‐collecting (i.e., p‐type) polysilicon contacts. It is found that such plasma processing offers excellent thickness control and superior structural integrity upon thermal annealing at 1000 °C, compared to state‐of‐the‐art wet‐chemical oxides. As a result, p‐type polysilicon contacts are achieved on n‐type c‐Si wafers that combine excellent surface passivation, resulting in an implied open‐circuit voltage exceeding 700 mV, with a contact resistance as low as 0.02 Ω cm2.

Firing-Stable PECVD SiOxNy/n-Poly-Si Surface Passivation for Silicon Solar Cells

“…The acronym polysilicon on oxide (POLO) stands for “poly-Si on oxide,” whereas TOPCon denotes “tunneling oxide passivating contact” . In terms of process technology, intrinsic or doped amorphous silicon (a-Si) layers are deposited by low-pressure chemical vapor deposition (LPCVD) , or plasma-enhanced chemical vapor deposition (PECVD) , on top of thermally, , wet-chemically, ,, or PECVD − grown SiO x . The conversion from amorphous to polycrystalline silicon (poly-Si) is done during a high-temperature annealing process .…”

Mass production of crystalline silicon solar cells with polysilicon‐based passivating contacts: An industrial perspective

“…Plasma-assisted oxidation has also been demonstrated. 20,21 Thermal oxidation is currently the most widely used in the mass production process design, where the equipment is well developed and processing technologies are easily adapted to the current silicon solar cell fabrication lines. The thin oxide layer can be prepared by a short thermal oxidation (from 1 to 5 min) at a temperature range of between 500 and 600 C. 22 This is the most common way of combining the oxidation process with the poly-Si thin film deposition process in a single lowpressure chemical vapour deposition (LPCVD) tube.…”

“…For the formation of this oxide layer on a production line, various solutions are available including thermal oxidation, wet oxidation and chemical vapour deposition (CVD). Plasma‐assisted oxidation has also been demonstrated 20,21 . Thermal oxidation is currently the most widely used in the mass production process design, where the equipment is well developed and processing technologies are easily adapted to the current silicon solar cell fabrication lines.…”

Poly‐SiOx Passivating Contacts with Plasma‐Assisted N2O Oxidation of Silicon (PANO‐SiOx)

“…To this end, research and development on the integration of such materials and PANO-SiO x via PECVD for c-Si surface passivation are appealing to PV community. [48,49] In this contribution, the application of PANO-SiO x /poly-SiO x passivating contacts is elaborated that are grown by PECVD. First, we reveal the relation between PECVD process conditions and PANO-SiO x properties such as the thickness and stoichiometry of SiO x .…”