Local Bonding Influence on the Band Edge and Band Gap Formation in Quaternary Chalcopyrites

• Published in: Advanced science Vol. 4; no. 9; pp. 1700080 - n/a
• Main Authors: Miglio, Anna, Heinrich, Christophe P., Tremel, Wolfgang, Hautier, Geoffroy, Zeier, Wolfgang G.
• Format: Journal Article
• Language: English
• Published: Germany John Wiley and Sons Inc 01-09-2017
• Subjects: band engineering; chalcopyrites; local bond influence; photovoltaics; thermoelectrics; chalcopyrites; local bond influence; band engineering; thermoelectrics; photovoltaics
• ISSN: 2198-3844; 2198-3844
• DOI: 10.1002/advs.201700080

Quaternary chalcopyrites have shown to exhibit tunable band gaps with changing anion composition. Inspired by these observations, the underlying structural and electronic considerations are investigated using a combination of experimentally obtained structural data, molecular orbital considerations, and density functional theory. Within the solid solution Cu2ZnGeS4−xSex, the anion bond alteration parameter changes, showing larger bond lengths for metal–selenium than for metal–sulfur bonds. The changing bonding interaction directly influences the valence and conduction band edges, which result from antibonding Cu–anion and Ge–anion interactions, respectively. The knowledge of the underlying bonding interactions at the band edges can help design properties of these quaternary chalcopyrites for photovoltaic and thermoelectric applications.
Changing bond lengths and bond strengths in quaternary chalcopyrites affects the bond overlap and band gaps. The Ge–chalcogen and Cu–chalogen bonds form the conduction and valence bands in quaternary chalcopyrites, respectively. Changing the anion content alters the bonding interaction and with it the band edges and band gaps.