Deep defects limiting the conversion efficiency of Sb₂Se₃ thin-film solar cells

Area of Science:

• Materials Science
• Solid State Physics
• Photovoltaics

Background:

• Quasi-one-dimensional (Q1D) antimony selenide (Sb2Se3) is a promising photovoltaic material.
• Sb2Se3 solar cells have stagnated in photoelectric conversion efficiency (PCE) due to unresolved intrinsic limitations.

Purpose of the Study:

• Investigate the intrinsic reasons for the PCE stagnation in Sb2Se3 solar cells.
• Explore the effects of growth conditions on Sb2Se3 thin film quality and device performance.
• Identify key defects limiting solar cell efficiency.

Main Methods:

• High-quality Q1D Sb2Se3 thin films prepared using vapor transport deposition.
• Analysis of bandedge electronic level structure.
• Investigation of carrier relaxation and recombination dynamics.

Main Results:

• Optimized Se-rich growth conditions significantly enhance Sb2Se3 crystal quality and carrier lifetime (up to ~8.3 μs).
• Se-rich conditions reduce deep selenium vacancies (VSe, i=1,3) but not a specific deep donor VSe.
• A deep donor VSe defect (~0.3 eV below conduction band) intrinsically limits PCE below ~7.63%.

Conclusions:

• Improving crystal quality and carrier lifetime via Se-rich conditions is beneficial.
• A specific deep donor selenium vacancy defect is the primary limitation for Sb2Se3 solar cell PCE.
• Further optimization to eliminate this deep donor defect is crucial for high-performance Sb2Se3 solar cells.