TITLE:
Pyroelectric Bi5-x(Bi2S3)39I12S: Fibonacci Superstructure, Synthesis Options and Solar Cell Potential
AUTHORS:
Hans Hermann Otto
KEYWORDS:
Hexagonal Bismuth Sulfide Iodide, Superstructure, Sub-Cell, Fibonacci Numbers Sequence, Pyroelectricity, Crystal Growth, Nano-Rods, Completely Inorganic Solar Cell, Twin-Cell, Photocatalyst
JOURNAL NAME:
World Journal of Condensed Matter Physics,
Vol.5 No.2,
April
27,
2015
ABSTRACT: Previously,
synthetic hexagonal bismuth sulfide iodide (polar space group P63, a
= 15.629(3) ?, c = 4.018(1) ?, Z = 2) has been described by the rather
unsatisfactory fractional formula Bi19/3IS9 [1]
08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370039000000
-[3]
08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000E0000005F005200650066003400310037003600350038003400370036000000
. A redetermination of the structure using old but reliable photographic
intensity data indicated the presence of additional split positions and reduced
atomic occupancies. From the observed pattern of this “averaged” structure a
consistent model of a superstructure with lattice parameters of a' = √13·a =
56.35(1) ?, c' = c, and a formula Bi5-x(Bi2S3)39I12S
emerged, with 2 formula units in a cell of likewise P63 space group.
Structural modulation may be provoked by the space the lone electron pair of Bi
requires. When Bi on the 0, 0, z position of the “averaged” cell is transferred
to two general six-fold sites and one unoccupied twofold one of the super-cell,
more structural stability is guaranteed due to compensation of its basal plane
dipole momentum. Owing to the limited intensity data available, more details of
the superstructure are not accessible yet. Some physical properties and solar
cell application are discussed together with suggestions of ambient temperature
synthesis routes of c-axis oriented nano-rod sheets.