Structural characterization, vibrational, optical properties and DFT investigation of a new luminescent organic–inorganic material: (C6H14N)3Bi2I9

Charge carrier localised in zero-dimensional (CH3NH3)3Bi2I9 clusters

“…Although there was a report on the indirect transition of band gap for MABI based on the density functional theory calculations that imply a split of conduction band 21, 23 , it should be noted that the absorption spectra of MABI is dependent on the orientation of crystals 24 , which is a strong indication of charge carrier localisation. The absorption spectrum of a MABI film shows an excitonic peak at 2.44 eV, which is slightly different to that of a similar (C 6 H 11 NH 3 ) 3 Bi 2 I 9 (2.47 eV 22, 27 ) containing (Bi 2 I 9 ) 3− clusters but with a larger organic group. Since this peak is usually assigned to the (Bi 2 I 9 ) 3− group 22 , the organic group does not contribute to the absorption at this energy level.…”

“…Since this peak is usually assigned to the (Bi 2 I 9 ) 3− group 22 , the organic group does not contribute to the absorption at this energy level. The lowest exciton state arises from excitations between the valence band, which consists of a mixture of Bi(6  s ) and I(5 p ) states, and the conduction band, which derives primarily from Bi(6 p ) states, and is confined zero-dimensionally in the bioctahedra Bi 2 I 9 3− 27 . Substitution of Cs or formanidinium on methylamonium (MA) site in MAPbI 3 has been shown to cause significant shift (larger than 100 meV) of the band edge 20, 28 , contrasting with MABI where the band gap is unchanged between Cs and MA 20 .

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Crystal and Electronic Structures of Complex Bismuth Iodides A3Bi2I9 (A = K, Rb, Cs) Related to Perovskite: Aiding the Rational Design of Photovoltaics

“…The close relationship to the perovskite structure is obvious from the coordination environment of the BiI 6 octahedra (Ortep plot with ellipsoids at 80%). could be clearly derived from the unit cell metrics (a = 14.6443 (19), b = 8.1787 (9), c = 20.885(2)Å, β = 90.421 (7) • ), the symmetry (Laue class 2/m) and the systematic zonal and serial extinction conditions (h0l reflections only present for h+l = 2n, h00 reflections only present for h = 2n). The solution of the crystal structure using direct methods led to the expected composition with four formula units per unit cell and all atoms occupying general positions (Wyckoff sites 4e).…”

Structural, vibrational and optical properties of a new self assembled organic–inorganic nanowire crystal (C6H14N)2[BiBr5]. A Density Functional Theory approach

“…Within the inorganic component, the Bismuth bromide octahedra can be connected in one of three ways: face, edge or corner sharing forming naturally isolated molecules (0D) [14][15][16], infinite chains (1D) [17] or two dimensional (2D) networks. In conjunction with some current research works on these metal halides compounds, the crystal structure, optical properties and vibrational studies of many organic-inorganic crystals have been investigated in our laboratory [18][19][20][21][22]. Our last two published papers have been devoted to the X-ray diffraction, optical properties and vibrational studies as well as DFT calculations of C 4 H 16 N 3 BiBr 6 [21] and (C 6 H 14 N) 3 Bi 2 I 9 [22].…”

“…In conjunction with some current research works on these metal halides compounds, the crystal structure, optical properties and vibrational studies of many organic-inorganic crystals have been investigated in our laboratory [18][19][20][21][22]. Our last two published papers have been devoted to the X-ray diffraction, optical properties and vibrational studies as well as DFT calculations of C 4 H 16 N 3 BiBr 6 [21] and (C 6 H 14 N) 3 Bi 2 I 9 [22]. For systems containing extended chains, typically [BiBr 4 ] À and [BiBr 5 ] 2 À such chains may be formed by one or two bridging halides, referred to as edge and corner-sharing polyhedra respectively.…”