Strong Correlation Between A-Site Cation Order and Self-Trapped Exciton Emission in 0D Hybrid Perovskites

Abstract

Metal halide perovskites and their derived materials have garnered significant attention as promising materials for solar cell and light-emitting applications. Among them, 0D perovskites, characterized by unique crystallographic/electronic structures with isolated metal halide octahedra, exhibit tremendous potential as light emitters with self-trapped exciton (STE). However, the modulation of STE emission characteristics in 0D perovskites primarily focuses on regulating B- or X-site elements. In this work, a lead-free compound, Sb³⁺-doped ((C₂H₅)₂NH₂)₃InCl₆ single crystal, which exhibits a high photoluminescence quantum yield, is synthesized, and with increasing temperature, the A-site organic cations undergo a transition from an ordered configuration to a disordered one, accompanied by a redshift in the STE emission. Furthermore, Hirshfeld surface calculations reveal that high temperatures enhance the thermal vibrations of SbCl₆ ^3- clusters and the octahedra distortion, which are responsible for the redshift. Since this thermally triggered transition of A-site order is reversible, it can be exploited for temperature-sensing applications. Overall, in this work, valuable insights are provided into the role of A-site cations in modulating STE emission and the design of efficient light emitters.

Keywords: A‐site cations; order–disorder transformations; self‐trapped excitons; temperature sensings; 0D perovskites.

Figure 1

a) Images of the Sb³⁺‐doped ((C₂H₅)₂NH₂)₃InCl₆ single crystal upon visible light (top) and 302 nm ultraviolet light (bottom) illumination. b) Crystal structure of the hybrid 0D ((C₂H₅)₂NH₂)₃InCl₆. c) Schematic diagram illustrating the Sb³⁺ substitution. d) Structure and configuration of the ((C₂H₅)₂NH₂)⁺ cations at room temperature. e) Powder X‐Ray diffraction (PXRD) patterns of hybrid 0D ((C₂H₅)₂NH₂)₃InCl₆ with and without Sb³⁺ doping. f) Ultraviolet−visible absorption spectra of hybrid 0D ((C₂H₅)₂NH₂)₃InCl₆ with increased Sb³⁺ dopant levels. g) PLQY of ((C₂H₅)₂NH₂)₃InCl₆:xSb³⁺ with different Sb³⁺ levels. The inset shows photograph of undoped ((C₂H₅)₂NH₂)₃InCl₆ (left) and ((C₂H₅)₂NH₂)₃InCl₆:0.42 Sb³⁺ (right) single crystals under UV light. h) Photoluminescence (PL) spectra of Sb³⁺‐doped ((C₂H₅)₂NH₂)₃InCl₆ excited at 282 nm. i) Photoluminescence excitation (PLE) spectra of Sb³⁺‐doped ((C₂H₅)₂NH₂)₃InCl₆ emission at 585 nm. j) PL decay and fitting curve of Sb³⁺‐doped ((C₂H₅)₂NH₂)₃InCl₆ at room temperature (RT).

Figure 2

a) Mapping of PL spectra of Sb³⁺‐doped ((C₂H₅)₂NH₂)₃InCl₆ at various temperatures from 80 to 360 K. b) Temperature‐dependent PL spectra collected from 80 to 360 K. c) The Commission Internationale de l’Eclairage (CIE) chromaticity coordinates for ((C₂H₅)₂NH₂)₃InCl₆:0.42%Sb³⁺ at 320 K (red pentagram) and 330 K (black pentagram). d) Time‐resolved PL decay curve collected on the sample at 80 K. e) FWHM of the PL spectra measured from 80 to 320 K. f) Integrated PL intensity as a function of 100/T.

Figure 3

a) Temperature‐dependent XRD patterns of ((C₂H₅)₂NH₂)₃InCl₆. b) XRD patterns between 13° and 25°. c) Crystal structure of the ((C₂H₅)₂NH₂)⁺ units at different temperatures. The 2D Hirshfeld fingerprint plots for SbCl₆ ³⁻ at d) LT (134 K), e) RT (296 K), and f) HT (330 K). The more intense color means a stronger interaction between SbCl₆ ³⁻ and the organic cations.

Figure 4

a) PL intensity retention over 50 cycles, with a vacuum chamber used to eliminate the effects of moisture. The inset shows photographs of the Sb³⁺‐doped ((C₂H₅)₂NH₂)₃InCl₆ sample at RT (blue box) and 330 K (red box) when exposed to UV light at 302 nm. b) Comparison of the PL emission of the initial powder and the one after 50 heating and cooling cycles. c) Schematic diagram of screen printing (left) and printed patterns revealed using the Sb³⁺‐doped ((C₂H₅)₂NH₂)₃InCl₆ precursor solutions on nonwoven fabrics exposed to visible light and images of the printed patterns at RT and 330 K under 302 nm UV light. (Middle) Images of the printed patterns at RT water and hot water under 302 nm UV light (right).