ARTICLE pubs.acs.org/JPCC
Hybrid Functionals Study of Band Bowing, Band Edges and Electronic Structures of Cd1xZnxS Solid Solution Jian-Chun Wu,† Jianwei Zheng,*,‡ Chelsey L. Zacherl,§ Ping Wu,‡ Zi-Kui Liu,§ and Rong Xu† †
School of Chemical and Biomedical Engineering, Nanyang Technological University, 62, Nanyang Drive, Singapore 637459 Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632 § Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, United States ‡
ABSTRACT: We have systematically studied band bowing, band edges, and electronic properties of both zinc-blende and wurtzite Cd1xZnxS solid solutions by using a special quasirandom structures approach combined with hybrid DFT calculations. Hybrid DFT gives a more accurate description of the lattice constants, formation enthalpies, and electronic structures of the parent semiconductors than standard DFT. Alloying CdS with ZnS causes a downward band bowing that is dominated by volume deformation. The conductionand valence- band edges straddle the redox potentials of (O2/H2O) and (H+/H2) over the whole Zn concentration range. The high photocatalytic activity of Cd1xZnxS is due to the elevation of the conduction band minimum (CBM). The optimal Zn content is around 0.5, determined as a result of balancing the elevation of the CBM and the widening of the band gap. The valence bandwidth increases with Zn content and thus raises the mobility of photogenerated holes, which may be related to photocorrosion and lead to the leaching of Zn in Cd1xZnxS photocatalyst during water splitting.
’ INTRODUCTION Cadmium sulfide (CdS) and zinc sulfide (ZnS) are two widely studied metal sulfides for photocatalytic water splitting.14 CdS is able to harvest visible light at wavelengths of
