Band Alignment and Surface Photo-Voltage Analysis of C-Si/Sio_x/Poly-Silicon Passivating-Contact Stacks Through X-Ray...

Area of Science:

• Materials Science
• Semiconductor Physics
• Renewable Energy

Background:

• Ultrathin silicon oxide (SiOₓ) layers and crystalline silicon (c-Si)/SiOₓ interfaces are crucial for tunnel-oxide passivated contacts (TOPcon) in high-efficiency silicon solar cells.
• Understanding the microscopic properties of these interfaces is vital for optimizing solar cell performance.

Purpose of the Study:

• Investigate the microscopic properties of c-Si/SiOₓ interfaces for TOPcon solar cells.
• Analyze the effects of substrate preparation (dry-plasma vs. wet SiOₓ) and annealing on SiOₓ stoichiometry and structure.
• Examine band-bending and junction photo-voltage (JPV) effects in these contact structures.

Main Methods:

• Utilized advanced photoemission techniques to analyze SiOₓ stoichiometry and microscopic structure.
• Investigated c-Si(100) substrates capped with p-type or n-type poly-silicon.
• Performed in-situ light exposure to study surface photovoltage and JPV effects.

Main Results:

• A decreased valence band offset (4.5 eV to 4.15 eV) was observed for dry SiOₓ compared to wet SiOₓ, correlating with sub-stoichiometric Si states.
• The JPV effect was found to be proportional to the quasi-Fermi level splitting within the c-Si wafer.
• Substrate preparation significantly influences the c-Si/SiOₓ interface properties.

Conclusions:

• The choice of SiOₓ deposition method (dry vs. wet) critically affects the valence band offset and interface properties.
• Advanced photoemission and JPV analysis provide insights into the electronic behavior of TOPcon structures.
• Optimizing SiOₓ layer properties is essential for enhancing the efficiency of silicon solar cells.