Zn(O,S) Buffer Layer for in Situ Hydrothermal Sb₂S₃ Planar Solar Cells

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Antimony-based solar cells, particularly Sb2(S,Se)3, are promising but typically use toxic Cadmium Sulfide (CdS) buffer layers.
• The narrow band gap of CdS leads to energy loss and reduced current density in devices.
• There is a need for efficient, non-toxic buffer layers in antimony-based solar cell technology.

Purpose of the Study:

• To evaluate Titanium Dioxide (TiO2) as a Cd-free buffer layer for hydrothermally grown Sb2S3 solar cells.
• To investigate the effectiveness of a Zinc Oxysulfide (Zn(O,S)) interlayer to improve Sb2S3 coverage on TiO2.
• To optimize the buffer layer structure for enhanced performance in Sb2S3 solar cells.

Main Methods:

• Hydrothermal deposition of Sb2S3 thin films.
• Fabrication of solar cells with TiO2 and TiO2/Zn(O,S) buffer layers.
• Surface morphology analysis and X-ray photoelectron spectroscopy (XPS) for binding energy.
• First-principles calculations (DFT) to study interface stability and electronic structure.

Main Results:

• TiO2 alone resulted in inhomogeneous Sb2S3 coverage.
• Inserting a Zn(O,S) layer enabled quasi-epitaxial growth of Sb2S3 on TiO2, confirmed by morphology and DFT.
• The Zn(O,S)/Sb2S3 junction showed favorable band alignment and interface contact.
• Solar cells with the TiO2/Zn(O,S) buffer layer achieved a champion efficiency of 3.70%, a significant increase from 0.54% with TiO2 alone.

Conclusions:

• Zn(O,S) acts as a crucial chemical bridge, enabling uniform Sb2S3 deposition and improving interface quality.
• The Zn(O,S)/Sb2S3 junction is structurally more stable and electronically superior to TiO2/Sb2S3.
• This work demonstrates a viable, high-performance, Cd-free buffer system for hydrothermally deposited Sb2S3 solar cells, paving the way for greener photovoltaic technologies.