Hybrid Functionals Study of Band Bowing, Band Edges and Electronic Structures of Cd_1–xZn_xS Solid Solution

Abstract

We have systematically studied band bowing, band edges, and electronic properties of both zinc-blende and wurtzite Cd1–x Zn x S 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 conduction- and valence- band edges straddle the redox potentials of (O2/H2O) and (H+/H2) over the whole Zn concentration range. The high photocatalytic activity of Cd1–x Zn x S 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 Cd1–x Zn x S photocatalyst during water splitting.

Facile synthesis of uniform ZnxCd1−xS alloyed hollow nanospheres for improved photocatalytic activities

“…7c. In particular, the Zn 0.5 Cd 0.5 S alloyed hollow nanospheres exhibited the best photocatalytic activities, which was in good agreement with the theorical calculation [36]. In addition, more than 95 % of RhB molecules in solution (15 mg/L) could be entirely decomposed in 40 min in presence of 10 mg Zn 0.5 Cd 0.5 S alloyed hollow nanospheres as shown in Fig.…”

Enhanced Photocatalytic Hydrogen‐Production Performance of Graphene–ZnxCd1−xS Composites by Using an Organic S Source

“…Tuning its bandgap width and band-edge position by construction of Zn 1Àx Cd x S solid solutions is an efficient method to address these problems. [13][14][15][16] For example, our previous work confirmed that enhanced photocatalytic capabilities were achieved in Zn x Cd 1Àx S solid solutions (x = 0.1, 0.3, 0.5, 0.7, and 0.9) compared with pure ZnS and CdS photocatalysts, especially for x = 0.5, owing to the balance between the bandgap width and the position of the conduction-band edge. [17] On the other hand, fabrication of composites with graphene is also a promising way to enhance the photoactivity of traditional semiconductor photocatalysts.…”

Graded Shells in Semiconductor Nanocrystals

“…In ZnSe/CdS interfacial alloying with a fast cation diffusion and a relatively slower anion diffusion leads to a region at the core with a composition close to Zn x Cd 1 − x Se and an inner shell composed of Zn 1 − x Cd x S. As the alloyed materials have band edges between those of the pure, binary compounds a potential trough at the valence band edge is formed in the sulfur-rich region that further confines the 1S hole to the core [28]. This effect can be enhanced by band bowing, which causes the band edges to change non-linear with composition x [41][42][43]. The effect is more pronounced when the gradient involves two anions.…”