Correction to:Inorganic-Cation Pseudohalide 2D Cs2Pb(SCN)2Br2 Perovskite Single Crystal (Adv. Mater., (2022), 34, (2104782), 10.1002/adma.2104782)
Journal
Advanced Materials
Date Issued
2023-01-01
Author(s)
Liao, Chwen Haw
Chen, Chiung Han
Bing, Jueming
Bailey, Christopher
Lin, Yi Ting
Pandit, Twishi Mukul
Granados, Laura
Zheng, Jianghui
Tang, Shi
Lin, Bi Hsuan
McCamey, Dane R.
Kennedy, Brendan J.
Ho-Baillie, Anita W.Y.
Abstract
Adv. Mater. 2022, 34, 2104782 DOI: 10.1002/adma.202104782 In this Correction, it is clarified that, contrary to the originally published article, CsPbBr3 is, in fact, present even in a freshly grown “non-degraded” Cs2Pb(SCN)2Br2 crystal as an impurity at a very small amount, <1% by volume, that can be detected optically but not by powder X-ray diffraction (pXRD), and its presence is throughout the crystal bulk. Cs2Pb(SCN)2Br2 thin film produces different absorbance than single crystal, with no CsPbBr3 absorbance in the film. The revised exciton binding energy (Eb) of Cs2Pb(SCN)2Br2 single is now 66 meV, the lowest for reported Ruddlesden–Popper phase 2D lead halide perovskite (n = 1). This results in a revised Figure 3 as shown below. 3 Corrected Figure (Figure presented.) Optical properties of Cs2Pb(SCN)2Br2 single crystal. a) Revised pseudo color map of temp–PL between 90K and 270K. b) Estimation of exciton binding energy from remeasured inverse PL intensity [1/I(T)] of Cs2Pb(SCN)2Br2 single crystal as a function of inverse temperature (1/T) plot fitted with an exponential decay (red dotted line). c) Remeasured photoluminescence decay curve of Cs2Pb(SCN)2Br2 single crystal with a biexponential fit. d) Revised summary chart of exciton binding energy (meV) versus bandgap (eV) for 2D (including this work), quasi-2D, and 3D perovskites. References can be found in the originally published article. e) Revised UV–vis absorption and PL spectra of Cs2Pb(SCN)2Br2 single crystal. f) Valence band from photoelectron spectroscopy (PES) unchanged from the published article. g) Revised Tauc plot from UV–vis absorption spectra for determining E0, now revised to be ≈2.52 eV. Inset: Cs2Pb(SCN)2Br2 band diagram with revised calculated conduction band at −2.95 eV. Results and Discussion Results of photoluminescence (PL) and absorbance spectra of fresh Cs2Pb(SCN)2Br2 single crystal grown within 6 h are shown in Figure C1a and Figure C1b. The measured PL spectrum (black marker) in Figure C1a shows that while a “blue” PL peak at 2.67 eV can be observed for Cs2Pb(SCN)2Br2, there is a broadening extended to lower energy. This is due to the presence of a weaker “green” PL peak at 2.34 eV for CsPbBr3. Figure C1a illustrates a simulated PL curve (red curve) that is the sum of a strong green peak and a weak blue peak. The green emission is weak because we believe the amount of CsPbBr3 present in a fresh “non-degraded” Cs2Pb(SCN)2Br2 crystal as an impurity is small. It is likely to be <1% by volume which is below the detection limit of the powder X-ray diffraction (pXRD) measurement (Figure C1c). While CsPbBr3 cannot be detected in the measured XRD pattern of our Cs2Pb(SCN)2Br2 crystal, it is sufficient to be observed via PL emission and UV–vis absorbance (probably due to the high PL quantum yield of CsPbBr3).[1] In the latter, a “green” absorbance shoulder can be observed (see blue curve in Figure C1b). We have also measured absorbance of surface etched Cs2Pb(SCN)2Br2 single crystal (red curve in Figure C1b). It can be seen that both the “green” absorbance shoulder can still be observed in the etched sample, suggesting that the small amount of CsPbBr3 impurity is present throughout the crystal bulk rather than just at the surface. C1 Figure (Figure presented.) a) The PL spectra of Cs2Pb(SCN)2Br2 single crystal measured experimentally (black dots) and simulated (red) which is the sum of a strong 2.67 eV blue emission (blue) and a weak 2.34 eV green emission (green). b) UV–vis absorbance of fresh (blue) and surface etched (red) Cs2Pb(SCN)2Br2 single crystal. The inset shows optical microscopy images of fresh and surface-etched Cs2Pb(SCN)2Br2 single crystal using DMSO/THF solutions with a 1/40 ratio, which produced the best etched “clean” surface. c) Powder XRD pattern of fresh Cs2Pb(SCN)2Br2 single crystal measured. d) The UV–vis absorbance spectrum of a Cs2Pb(SCN)2Br2 thin film. To fabricate the thin film sample for absorbance measurement, we dissolved the fresh Cs2Pb(SCN)2Br2 single crystal into a precursor. The results, shown in Figure C1d, show a sharp “blue” absorbance peak, in agreement to that reported by Chu et al.[2] It is likely that the Cs2Pb(SCN)2Br2 fully crystallizes at the annealing temperature used (75 °C) in the thin film, at which CsPbBr3 is unable to do so as it requires a temperature of 180 °C. Finally, we determined the exciton binding energy (Eb) of Cs2Pb(SCN)2Br2 single crystal from the temperature-dependent 2.67 eV PL peak (Figure C2) instead of the 2.34 eV peak. Parameters for fitting the temperature-dependent PL can be found Table C1. Eb is calculated to be 66 meV, lower than those as determined in the initially published paper (160 meV). The value is now the lowest for reported RP-phase 2D lead halide perovskite (n = 1). C1 Table Parameters for fitting temp–PL of the Cs2Pb(SCN)2Br2 single crystal to determine binding energy (Table presented.) C2 Figure (Figure presented.) Temperature-dependent PL (temp–PL) of Cs2Pb(SCN)2Br2 single crystal measured at 10 K intervals from 90 K to 270 K for exciton binding energy calculation. The bandgap of Cs2Pb(SCN)2Br2 is now revised to be 2.59 eV (Eg = E0 + Eb = 2.52 + 0.07 eV) where the exciton ground state (E0) of 2.52 eV was determined using the Kubelka–Munk method.[3] The valence and conduction bands are now −5.54 and −2.95 eV, respectively, similar to the reported Cs2Pb(SCN)2Br2 polycrystalline film.[2,4] The effective carrier lifetime must also be revised to be ≈0.20 ns, which is consistent with those reported for typical 2D lead halide perovskites.[5] Parameters for fitting the time-resolved photoluminescence (trPL) (Corrected Figure 3c) can be found in Table C2. All of the revised results are now captured in the above Corrected Figure 3—a corrected version of the original Figure 3 in the published article. C2 Table Parameters for fitting the trPL dynamics of the Cs2Pb(SCN)2Br2 single crystal to determine carrier lifetime (Table presented.) Acknowledgements The authors would like to thank Xujie Lü, Lingling Mao, Haiming Zhu and their teams from the Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai and the Department of Chemistry, Southern University of Science and Technology, Shenzhen and the Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang, China for pointing out the possible presence of CsPbBr3 in Cs2Pb(SCN)2Br2, which indeed was found by our further experiments, albeit small.
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