Shallow dopants and compensating centers in antimony triselenide

• Applicant: Professor Dr. Eduard Lavrov
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 513760901

In recent years, antimony triselenide (Sb2Se3) has attracted increasing attention as a versatile chalcogenide semiconductor for applications ranging from photovoltaics and photoelectrochemical devices to photodetectors, thermoelectrics, batteries, and phase-change materials. Among these, Sb2Se3 stands out as an efficient, environmentally benign, stable, and low-cost absorber material for thin-film solar cells. Continuous progress in synthesis and device engineering has led to a remarkable increase in the power conversion efficiency of antimony chalcogenide-based solar cells from about 1% to over 10% within the past decade. Defects and impurities play a decisive role in determining the performance of semiconductor materials. A prime example is CdTe thin-film photovoltaics, where the deliberate incorporation of dopants such as Cu, Cl, O, and S has raised efficiencies from ∼2% in the early 1990s to ∼23% today. In contrast, the defect physics of Sb2Se3 remains largely unexplored. Sb2Se3 is often semi-insulating, which prevents control over electrical conductivity—a key requirement for virtually all practical applications. It remains unclear which native defects, impurities, or defect complexes contribute to charge-carrier generation, and which act as trap states or recombination centers. The present project, along with its proposed continuation, aims to close this knowledge gap. The primary objective of the continuation project is to establish a fundamental understanding of the nature and behavior of shallow dopants and compensating defect complexes in single-crystalline Sb2Se3 using optical and electrical spectroscopies. The work will focus on five technologically relevant elements: chlorine, cadmium, hydrogen, oxygen, and sulfur. Based on key results from the preceding project phase, the first three will be given the highest priority: chlorine and cadmium, identified as efficient donor and acceptor dopants, respectively, to enable controllable and stable n- and p-type conductivity; and hydrogen, a ubiquitous impurity capable of passivating p-type conductivity. The defect studies will address spectroscopic fingerprints, electrical activity, thermal stability, kinetic behavior, and the interactions of dopants and defect complexes with native point defects. By elucidating these mechanisms, the project will advance the fundamental understanding of defect physics in Sb2Se3 and strengthen the scientific foundation for improving the performance of antimony chalcogenide-based materials in photovoltaics and other emerging applications.

• DFG Programme: Research Grants