Some Natural Three-and Lower-Dimensional Semiconductor Systems with Metal-Halide Units

Abstract

The structural, optical and related properties (i.e. photoluminescence, photoconductivity etc.) of some natural three- and lower-dimensional semiconductor systems based on metal halides are briefly reviewed and some new results are reported. A blue shift of the excitonic bands was observed by decreasing the dimensionality or the size of the materials active part. The results are similar to those obtained from conventional semiconductor systems (e.g. GaAs, CdS, PbI2) by decreasing artificially the dimensionality or decreasing the size.

Structure and Optical Properties of Several Organic−Inorganic Hybrids Containing Corner-Sharing Chains of Bismuth Iodide Octahedra

“…The peak is also observable at room temperature, indicating a large exciton binding energy (estimated to be ∼300 meV). In (C 6 H 5 C 2 H 4 NH 3 ) 4 BiI 7 ·H 2 O, which contains smaller isolated BiI 6 3- octahedra, the exciton peak falls at slightly higher energy (474 nm) . For (H 2 DAH)BiI 5 , with its extended BiI 5 2- chains, the peak red-shifts to 554 nm, while in the more two-dimensional BiI 3 structure, the direct exciton transition occurs at approximately 600 nm .…”

“…In (C 6 H 5 C 2 H 4 NH 3 ) 4 BiI 7 ‚H 2 O, which contains smaller isolated BiI 6 3octahedra, the exciton peak falls at slightly higher energy (474 nm). 11 For (H 2 DAH)-BiI 5 , with its extended BiI 5 2chains, the peak red-shifts to 554 nm, 12 while in the more two-dimensional BiI 3 structure, the direct exciton transition occurs at approximately 600 nm. 31 These results apparently reflect the effect of the inorganic framework dimensionality on the electronic structure of the material.…”

“…The BiI 6 octahedra may join to form discrete (i.e., mononuclear) or extended (i.e., polynuclear) inorganic networks of corner-, edge-, or facesharing octahedra, leading to an extensive family of bismuth halogenoanions (e.g., BiX 4 -, BiX 5 2-, BiX 6 3-, Bi 2 X 9 3-, Bi 2 X 11 5-, Bi 3 X 12 3-, Bi 4 X 18 6-, Bi 5 X 18 3-, Bi 6 X 22 4-, and Bi 8 X 30 6-). 10 Among the bismuth iodides, isolated BiI 6 octahedra are found in (C 6 H 5 -CH 2 CH 2 NH 3 ) 4 BiI 7 ‚H 2 O, 11 with iodide anions and water molecules interposed between the octahedra in the inorganic layers of the structure. Chains of corner-sharing octahedra are found in (H 3 NC 6 H 12 NH 3 )BiI 5 .…”

Organic−Inorganic Perovskites Containing Trivalent Metal Halide Layers: The Templating Influence of the Organic Cation Layer

“…Bismuth(III)/antimony(III) halide structures generally consist of distorted MX 6 octahedra, which share corners, edges, or faces to form discrete or extended inorganic networks. Among the bismuth iodides, isolated BiI 6 octahedra are found in (C 6 H 5 CH 2 CH 2 NH 3 ) 4 BiI 7 ·H 2 O, with iodide anions and water molecules interposed between the octahedra in the inorganic layers of the structure. Chains of corner-sharing octahedra are found in (H 3 NC 6 H 12 NH 3 )BiI 5 , as well as in analogous BiI 5 2- systems containing the longer and more complex organic molecules 1,6-bis[5‘-(2‘ ‘-aminoethyl)-2‘-thienyl]hexane (AETH) and 1,12-dodecanediamine (DDDA) .…”

Trimethylsulfonium Lead Triiodide: An Air-Stable Hybrid Halide Perovskite

“…Values in the range of 0.8 < t < 1 favor 3D structures with edge-sharing [PbI 6 ] octahedra (e.g., CH 3 NH 3 PbI 3 ). For t < 0.8, the NH 4 CdCl 3 -type structure is formed, whereas for t > 1, 1D or 2D structures with face-sharing [PbI 6 ] octahedra are formed. − Such low-dimensionality perovskites are also good candidates for tandem solar cells, and it was recently observed that the 2D semiconducting (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 ) n −1 Pb n I 3 n +1 ( n = 1, 2, 3, 4) compounds exhibit good long-term stability in air while maintaining their efficiency in perovskite solar cells …”