Colloidal Synthesis and Photophysics of M₃Sb₂I₉ (M=Cs and Rb) Nanocrystals: Lead‐Free Perovskites

Abstract

Herein we report the colloidal synthesis of Cs 3 Sb 2 I 9 and Rb 3 Sb 2 I 9 perovskite nanocrystals,a nd explore their potential for optoelectronic applications.D ifferent morphologies,s uch as nanoplatelets and nanorods of Cs 3 Sb 2 I 9 ,a nd spherical Rb 3 Sb 2 I 9 nanocrystals were prepared. All these samples show band-edge emissions in the yellow-red region. Exciton many-body interactions studied by femtosecond transient absorption spectroscopyofCs 3 Sb 2 I 9 nanorods reveals characteristic second-derivative-type spectral features,suggesting red-shifted excitons by as much as 79 meV.Ah igh absorption cross-section of ca. 10 À15 cm 2 was estimated. The results suggest that colloidal Cs 3 Sb 2 I 9 and Rb 3 Sb 2 I 9 nanocrystals are potential candidates for optical and optoelectronic applications in the visible region, though ab etter control of defect chemistry is required for efficient applications. Figure 1. a) Schematic representation of the relationship among the perovskitec rystal structures of i) 3D CsMI 3 (M = Pb 2+ /Sn 2+ ), ii)2D Cs 3 Sb 2 I 9 ,and iii)0DCs 2 SnI 6 .b)Schematic representation of the synthesis of Cs 3 Sb 2 I 9 NPLs and Cs 3 Sb 2 I 9 NRs. ODE = 1-octadecene, OnA = octanoic acid, OAm = oleylamine.[*] J. Pal, S. Manna, [+] A. Nag

Lead‐Free Halide Perovskite Nanocrystals: Crystal Structures, Synthesis, Stabilities, and Optical Properties

“…Colloidal Cs 3 Sb 2 I 9 (NPLs and NRs) were prepared via the hot injection method. [64] Thel ength of the Cs 3 Sb 2 I 9 NRs was found to be larger than their excitonic Bohr diameters. However,t he thickness (1.5 nm) of the Cs 3 Sb 2 I 9 NPLs is sufficiently small such that they still experience aq uantum confinement effect, resulting in ablue-shift in the optical gap.…”

“…Thes econd is the two-dimensional (2D) layered perovskite structure (layered phase) of corrugated layers with partially corner sharing [BX 6 ] 3À octahedra, which can be formed by removing 1/3 of the Bsites from an 3D parent perovskite. [63][64][65] Notably, introduction of smaller Rb + and NH 4 + as Acations can effectively stabilize the structure in its layered form. [64,67] In the case of Bi-based halide perovskite,C s 3 Bi 2 I 9 NCs and MA 3 [53] Copyright2 017, Science PublishingGroup.…”

“…[63][64][65] Notably, introduction of smaller Rb + and NH 4 + as Acations can effectively stabilize the structure in its layered form. [64,67] In the case of Bi-based halide perovskite,C s 3 Bi 2 I 9 NCs and MA 3 [53] Copyright2 017, Science PublishingGroup. c) Cubic structure of CsSnCl 3 NCs.…”

“…Cs 3 Sb 2 I 9 NCs were prepared via the hot-injection method for visible-light optoelectronics. [64] Themorphology tuning of Cs 3 Sb 2 I 9 NCs to yield NPLs and NRs was realized by varying the reaction temperature,asdepicted in Figure 12 b. Recently, uniform colloidal Cs 3 Sb 2 Cl 9 perovskite NWs (with lengths up to several microns) have been obtained by tuning the precursors and ligands in the hot injection method.…”

Perovskite Solar Absorbers: Materials by Design

“…Although Cs 3 Sb 2 I 9 is a perovskite derivative, these calculations indicate that the defect properties are quite different from that in MAPbI 3 . Therefore, the defect properties of Cs 3 Sb 2 I 9 could be a main issue that requires careful control toward PV applications …”