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

Adv Sci (Weinh). 2017 May 22;4(9):1700080. doi: 10.1002/advs.201700080. eCollection 2017 Sep.


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-x Se x , 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.

Keywords: band engineering; chalcopyrites; local bond influence; photovoltaics; thermoelectrics.