TY - JOUR
T1 - From 0D Cs 3 Bi 2 I 9 to 2D Cs 3 Bi 2 I 6 Cl 3
T2 - Dimensional Expansion Induces a Direct Band Gap but Enhances Electron-Phonon Coupling
AU - McCall, Kyle M.
AU - Stoumpos, Constantinos C.
AU - Kontsevoi, Oleg Y.
AU - Alexander, Grant C.B.
AU - Wessels, Bruce W.
AU - Kanatzidis, Mercouri G.
N1 - Funding Information:
This work is supported by the Department of Homeland Security ARI program under the grant 2014-DN-077-ARI086-01. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. This work made use of the IMSERC at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the State of Illinois and International Institute for Nanotechnology (IIN). This work made use of the SPID facility of Northwestern University’s NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN.
Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/4/9
Y1 - 2019/4/9
N2 - Alternative all-inorganic halide perovskites are sought to replace the hybrid lead halide perovskites because of their increased stability. Here, the (111)-oriented defect perovskite family A 3 M 2 X 9 based on trivalent M 3+ is expanded through the use of mixed halides, resulting in Cs 3 Bi 2 I 6 Cl 3 . This compound shares the (111)-oriented 2D bilayer structure of α-Cs 3 Sb 2 I 9 (space group P3..m1), with Cl occupying the bridging positions of the bilayers and I in the terminal sites, in contrast to the parent compound Cs 3 Bi 2 I 9 , which consists of 0D molecular [Bi 2 I 9 ] 3- dimers. The increased dimensionality induces a direct band gap as calculated by density functional theory but has an absorption edge of 2.07 eV, nearly identical to the indirect band gap compound Cs 3 Bi 2 I 9 . Intriguingly, there is a remarkable lack of Cl orbital contribution to the band edge states of Cs 3 Bi 2 I 6 Cl 3 , despite Bi-Cl bonds binding all octahedra together. This highlights the importance of interlayer interactions in the defect perovskite family, which enhances the effective dimensionality of these 2D and 0D materials and may improve their optoelectronic performance. However, these changes in the excitonic absorption do not reflect free excitons, as Cs 3 Bi 2 I 6 Cl 3 exhibits broad photoluminescence as a result of self-trapped excitons, which appear to be universal in the (111)-oriented defect perovskites.
AB - Alternative all-inorganic halide perovskites are sought to replace the hybrid lead halide perovskites because of their increased stability. Here, the (111)-oriented defect perovskite family A 3 M 2 X 9 based on trivalent M 3+ is expanded through the use of mixed halides, resulting in Cs 3 Bi 2 I 6 Cl 3 . This compound shares the (111)-oriented 2D bilayer structure of α-Cs 3 Sb 2 I 9 (space group P3..m1), with Cl occupying the bridging positions of the bilayers and I in the terminal sites, in contrast to the parent compound Cs 3 Bi 2 I 9 , which consists of 0D molecular [Bi 2 I 9 ] 3- dimers. The increased dimensionality induces a direct band gap as calculated by density functional theory but has an absorption edge of 2.07 eV, nearly identical to the indirect band gap compound Cs 3 Bi 2 I 9 . Intriguingly, there is a remarkable lack of Cl orbital contribution to the band edge states of Cs 3 Bi 2 I 6 Cl 3 , despite Bi-Cl bonds binding all octahedra together. This highlights the importance of interlayer interactions in the defect perovskite family, which enhances the effective dimensionality of these 2D and 0D materials and may improve their optoelectronic performance. However, these changes in the excitonic absorption do not reflect free excitons, as Cs 3 Bi 2 I 6 Cl 3 exhibits broad photoluminescence as a result of self-trapped excitons, which appear to be universal in the (111)-oriented defect perovskites.
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U2 - 10.1021/acs.chemmater.9b00636
DO - 10.1021/acs.chemmater.9b00636
M3 - Article
AN - SCOPUS:85063406906
VL - 31
SP - 2644
EP - 2650
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 7
ER -