Optimization of CZTSe Thin Films Using Sequential Annealing in Selenium and Tin-Selenium Environments

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Cu₂ZnSnSe₄ (CZTSe) is a promising photovoltaic material due to its earth-abundant composition and favorable optoelectronic properties.
• Developing efficient fabrication methods for high-quality CZTSe thin films is crucial for advancing thin-film solar cell technology.

Purpose of the Study:

• To investigate the effect of a two-step annealing process on the structural, morphological, and optoelectronic properties of CZTSe thin films.
• To optimize annealing atmospheres for improved CZTSe phase formation and material quality.

Main Methods:

• Fabrication of CZTSe thin films via a two-step annealing of Cu/SnSe₂/ZnSe stacks.
• Utilized sequential annealing in selenium (Se) or tin-selenium (Sn+Se) atmospheres.
• Characterization using GIXRD, Raman spectroscopy, SEM, EDS, and Hall measurements.

Main Results:

• Successfully synthesized kesterite CZTSe phase, with secondary phases identified in some samples.
• Annealing in Sn+Se atmosphere, especially in the second step, promoted larger grain growth.
• Tunable band gap (1.09–1.63 eV) and p-type conductivity (10¹⁶–10²³ cm^-3) were achieved.

Conclusions:

• The two-step annealing process is effective for CZTSe thin film fabrication.
• The Sn+Se atmosphere plays a critical role in optimizing CZTSe properties for solar cell applications.