TY - JOUR

T1 - Composition and electronic structure of SiOx/TiOy/Al passivating carrier selective contacts on n‑type silicon solar cells

AU - Flathmann, Christoph

AU - Meyer, Tobias

AU - Titova, Valeriya

AU - Schmidt, Jan

AU - Seibt, Michael

N1 - Funding Information: The work of C.F., T.M. and M.S. was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—217133147/SFB 1073, project B02. The work of V.T. and J.S. was supported by the State of Lower Saxony and the German Federal Environmental Foundation (DBU). The use of equipment of the “Collaborative Laboratory and User Facility for Electron Microscopy” (CLUE, Göttingen) is gratefully acknowledged. We acknowledge support by the Open Access Publication Funds of the Göttingen University.

PY - 2023

Y1 - 2023

N2 - Carrier-selective and passivating SiOx/TiOy heterocontacts are an attractive alternative to conventional contacts due to their high efficiency potentials combined with relatively simple processing schemes. It is widely accepted that post deposition annealing is necessary to obtain high photovoltaic efficiencies, especially for full area aluminum metallized contacts. Despite some previous high-level electron microscopy studies, the picture of atomic-scale processes underlying this improvement seems to be incomplete. In this work, we apply nanoscale electron microscopy techniques to macroscopically well-characterized solar cells with SiOx/TiOy/Al rear contacts on n-type silicon. Macroscopically, annealed solar cells show a tremendous decrease of series resistance and improved interface passivation. Analyzing the microscopic composition and electronic structure of the contacts, we find that partial intermixing of the SiOx and TiOy layers occurs due to annealing, leading to an apparent thickness reduction of the passivating SiOx. However, the electronic structure of the layers remains clearly distinct. Hence, we conclude that the key to obtain highly efficient SiOx/TiOy/Al contacts is to tailor the processing such that the excellent chemical interface passivation of a SiOx layer is achieved for a layer thin enough to allow efficient tunneling through the layer. Furthermore, we discuss the impact of aluminum metallization on the above mentioned processes.

AB - Carrier-selective and passivating SiOx/TiOy heterocontacts are an attractive alternative to conventional contacts due to their high efficiency potentials combined with relatively simple processing schemes. It is widely accepted that post deposition annealing is necessary to obtain high photovoltaic efficiencies, especially for full area aluminum metallized contacts. Despite some previous high-level electron microscopy studies, the picture of atomic-scale processes underlying this improvement seems to be incomplete. In this work, we apply nanoscale electron microscopy techniques to macroscopically well-characterized solar cells with SiOx/TiOy/Al rear contacts on n-type silicon. Macroscopically, annealed solar cells show a tremendous decrease of series resistance and improved interface passivation. Analyzing the microscopic composition and electronic structure of the contacts, we find that partial intermixing of the SiOx and TiOy layers occurs due to annealing, leading to an apparent thickness reduction of the passivating SiOx. However, the electronic structure of the layers remains clearly distinct. Hence, we conclude that the key to obtain highly efficient SiOx/TiOy/Al contacts is to tailor the processing such that the excellent chemical interface passivation of a SiOx layer is achieved for a layer thin enough to allow efficient tunneling through the layer. Furthermore, we discuss the impact of aluminum metallization on the above mentioned processes.

UR - http://www.scopus.com/inward/record.url?scp=85148548913&partnerID=8YFLogxK

U2 - 10.1038/s41598-023-29831-2

DO - 10.1038/s41598-023-29831-2

M3 - Article

C2 - 36813814

AN - SCOPUS:85148548913

VL - 2023

JO - Scientific reports

JF - Scientific reports

SN - 2045-2322

IS - 13

M1 - 3124

ER -