Solution-Based Preparation of Cu₂ZnSn(S,Se)₄ for Solar Cells—Comparison of SnSe₂ and Elemental Se as Chalcogen Source

Abstract

Thin-film solar cells with a Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ZnSn(S,Se) <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> absorber were prepared in a two-step process based on a metal salt solution that is deposited onto a molybdenum-coated substrate and subsequently annealed in a selenium-containing nitrogen atmosphere. The solar cell performance could be improved to efficiencies above 10% without usage of the highly toxic hydrazine or H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Se gas. A crucial step for obtaining high-quality absorbers is the incorporation of Se during the annealing process. Therefore, a detailed investigation of elemental Se and SnSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as chalcogen sources with various process parameters was performed. SnSe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> resulted in absorbers with improved morphology but could achieve only medium efficiencies, whereas elemental Se forms a triple-layer structure with efficiencies of up to 10.3%.