Electron Transport Layer Engineering Induced Carrier Dynamics Optimization for Efficient Cd-Free Sb₂ Se₃ Thin-Film...

Area of Science:

• Materials Science
• Renewable Energy

Background:

• Antimony selenide (Sb₂ Se₃) is a promising photovoltaic material due to its excellent optoelectronic properties, cost-effectiveness, and environmental friendliness.
• The widespread use of toxic cadmium sulfide (CdS) as an electron transport layer (ETL) hinders the commercialization of efficient Sb₂ Se₃ solar cells.

Purpose of the Study:

• To develop an effective, green, and cadmium-free ETL for Sb₂ Se₃ solar cells.
• To optimize the Sb₂ Se₃ /ETL heterojunction interface and improve the quality of the Sb₂ Se₃ absorber layer.

Main Methods:

• Atomic layer deposition (ALD) was used to deposit a tin oxide (SnO_x) ETL.
• Post-annealing treatments were employed to optimize the functional layers and heterojunction properties.
• Characterization of the SnO_x ETL, Sb₂ Se₃ /SnO_x heterojunction, and Sb₂ Se₃ absorber layer was performed.

Main Results:

• The SnO_x ETL exhibited enhanced nano-crystallinity, higher carrier density, and reduced defect groups.
• The Sb₂ Se₃ /SnO_x heterojunction showed improved interface performance and a desirable "spike-like" band alignment.
• The Sb₂ Se₃ absorber layer quality was enhanced with passivated bulk defects and prolonged carrier lifetime.
• The fabricated Cd-free solar cell achieved a record efficiency of 7.39% for substrate-structured Sb₂ Se₃ devices.

Conclusions:

• The developed SnO_x ETL and post-annealing strategy effectively enhance carrier separation and transport while suppressing recombination.
• This work presents a viable strategy for developing environmentally friendly and commercially viable Sb₂ Se₃ photovoltaic devices.
• The record efficiency achieved demonstrates the potential of Cd-free ETLs in advancing Sb₂ Se₃ solar cell technology.