부산대학교 도서관

The ternary chalcogenide, ZnIn2S4 is known to exhibit various polymorphic expressions: from the cubic spinel phase to various polytypic layered hexagonal structures. Notwithstanding numerous recent studies on the superior photocatalytic activities of hexagonal ZnIn2S4, it remains unclear how the polymorphic expressions in this materials may influence its physiochemical properties. Thus, revisiting and addressing the open questions on their intrinsic atomic and electronic structure properties in relation to their photoactivity is main intention of this work. Here, we systematically perform first-principles density-functional theory calculations to examine the crystal structures of layered hexagonal ZnIn2S4 and charge defect structure of IIb. Based on the compelling evidence from lattice dynamics, chemical bonding, and optoelectronic structure analysis, we propose a revised atomic structure for the IIa polymorph and explain why the previously acclaimed structure proposed in experiments must be disputed. Furthermore, from band alignment calculations, we rationalize that all hexagonal polymorphs of ZnIn2S4 are indeed photocathode materials.