|Title:||Stable, color-tunable 2D SCN-based perovskites: Revealing the critical influence of an asymmetric pseudo-halide on constituent ions||Authors:||Li C.-H.
|Issue Date:||2019||Journal Volume:||11||Journal Issue:||6||Start page/Pages:||2608-2616||Source:||Nanoscale||Abstract:||
Two-dimensional (2D) layered perovskites (A n+1 B n X 3n+1 , n = 1, 2, ?) have recently attracted significant research interest because of their enhanced ambient stability compared to their conventional 3D counterparts. In addition to the common A-site cation engineering, using an asymmetric pseudo-halide anion, SCN - , in the anion X-site has been recently proven to be another effective approach to constitute 2D perovskites. Among these, 2D (MA) 2 Pb(SCN) 2 I 2 was the most widely investigated and was considered to be a promising material owing to its good optoelectronic properties; however, its poor stability has aroused concerns in recent researches. In this study, systematical composition engineering of A 2 Pb(SCN) 2 X 2 (A = FA + , MA + , Cs + and X = Br - , I - ) was conducted. Our results revealed that the linear SCN - anion dictates critical restrictions on the constituent ions of its derived 2D framework (PbX 4 (SCN) 2 ), which has not yet been extensively discussed. We demonstrated that using a smaller Cs + cation can afford a more favorable 2D structure compared with the MA + cation. Cs 2 Pb(SCN) 2 I 2 was revealed to possess improved stability and photo-response compared to (MA) 2 Pb(SCN) 2 I 2 . Interestingly, Cs 2 Pb(SCN) 2 I 2 and (MA) 2 Pb(SCN) 2 I 2 appear to possess distinct electronic band structures. This is indicated by their discrepant photoluminescence spectra, in which the former exhibits a rather intense singlet emission at room temperature in contrast with the latter, which shows a dominant emission associated with triplet or defective states. Furthermore, using a smaller Cs + cation enables facile replacement of a smaller halide anion. A series of mixed-halide 2D Cs 2 Pb(SCN) 2 (I 1-x Br x ) 2 (x = 0, 1/3, 1/2, 2/3, 1) with varying vivid colors was explored by both calculation and experimental efforts to corroborate the enhanced stability when the x value increases. The results revealed in this study might represent a novel discovery of an inherent trait of the 2D SCN-based perovskites and also suggest that the all-inorganic 2D Cs 2 Pb(SCN) 2 X 2 perovskite system is a promising class of materials with good stability and color-tunability that deserves further exploration. ? 2019 The Royal Society of Chemistry.
|Appears in Collections:||化學工程學系|
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.