Comparing the Gettering Effect of Heavily Doped Polysilicon Films and Its Implications for Tunnel Oxide‐Passivated Contact Solar Cells. Issue 8 (2nd August 2022)

• Record Type: Journal Article
• Authors: Yang, Zhongshu; Krügener, Jan; Feldmann, Frank; Polzin, Jana-Isabelle; Steinhauser, Bernd; Aleshin, Matvei; Le, Tien T.; Macdonald, Daniel; Liu, AnYao
• Is Part Of: Solar RRL. Volume 7:Issue 8(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-02
• Subjects: gettering -- iron -- polysilicon/oxide passivating contacts -- segregation coefficient -- silicon solar cells; Solar energy -- Periodicals; Photovoltaic power generation -- Periodicals; Solar energy -- Research -- Periodicals; Photovoltaic power generation -- Research -- Periodicals; Periodicals; 333.7923
• DOI: 10.1002/solr.202200578
• Languages: English
• ISSNs: 2367-198X

Abstract

Abstract : In addition to excellent surface passivation and carrier selectivity, the structure based on the heavily doped polysilicon layer on an ultrathin silicon oxide interlayer also demonstrates strong impurity gettering effects. Herein, the gettering strength of a range of phosphorus‐ or boron‐doped polysilicon films from different fabrication techniques is assessed and compared. Iron, one of the most common metallic impurities in silicon, is used as a tracer impurity to quantify the gettering strength (segregation coefficient). A comparison of the experimental results to the literature, combined with measurements of the electrically active and inactive dopant concentrations, enables us to suggest the main gettering mechanisms in different polysilicon films. The differences in the segregation coefficients of the phosphorus‐doped polysilicon films for iron are within one order of magnitude, in spite of their different combinations of gettering mechanisms. On the other hand, boron‐doped polysilicon films show a large variation in their gettering effects, although the predominant gettering mechanisms are all attributed to electrically inactive boron, according to the current understanding of the gettering mechanisms from the literature. Finally, the impact of different polysilicon gettering effects on the efficiency of tunnel oxide‐passivated contact (TOPCon) cells is simulated and discussed. Abstract : Heavily doped polysilicon passivating contacts remove Fe from the silicon wafer bulk to the polysilicon gettering sink. The polysilicon films from different fabrication techniques have their own properties. Herein, the gettering effects of different polysilicon films are compared, the underlying gettering mechanisms are suggested, and their impact on tunnel oxide‐passivated contact cell performance is simulated.