Work

Ligand-Hole in [SnI6] Unit and Origin of Band Gap in Photovoltaic Perovskite Variant Cs2SnI6

Year: 2015

Type: article

Abstract: Cs2SnI6, a variant of perovskite CsSnI3, is gaining interest as a photovoltaic material. Based on a simple ionic model, it is expected that Cs2SnI6 is composed of Cs+, I−, and Sn4+ ions and that the band gap is primarily made of occupied I− 5p6 valence band maximum (VBM) and unoccupied Sn4+ 5s conduction band minimum (CBM) similar to SnO2. In this work, we performed density functional theory (DFT) calculations and revealed that the real oxidation state of the Sn ion in Cs2SnI6 is +2 similar to CsSnI3. The +2 oxidation state of Sn originates from 2 ligand holes (L+) in the [SnI6]2− octahedron unit, where the ligand [I6] cluster has the apparent [I66−L+2]4− oxidation state, because the band gap is formed mainly by occupied I 5p VBM and unoccupied I 5p CBM. The +2 oxidation state of Sn and the band gap originate from the intracluster hybridization and stabilized by the strong covalency of the Sn–I bonds.

Source: Bulletin of the Chemical Society of Japan

DOI: 10.1246/bcsj.20150110

Authors: Zewen Xiao, Hechang Lei, Xiao Zhang, Yuanyuan Zhou, Hideo Hosono, Toshio Kamiya

Institutions: Tokyo Institute of Technology, Renmin University of China, Brown University

Language: English

Topic: Perovskite Materials and Applications

Subfield: Electrical and Electronic Engineering

Field: Engineering

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, Ministry of Education, Culture, Sports, Science and Technology, Tokodai Institute for Element Strategy, Division of Materials Research

Awards: G1884867845, Ceramics Science of New Solid-State Solar Cells