Stable, color-tunable 2D SCN-based perovskites: revealing the critical influence of an asymmetric pseudo-halide on constituent ions. Issue 6 (25th January 2019)

• Record Type: Journal Article
• Authors: Li, Chia-Hsin; Tsai, Chang-Che; Liao, Ming-Yun; Su, Yu-An; Lin, Shiang-Tai; Chueh, Chu-Chen
• Is Part Of: Nanoscale. Volume 11:Issue 6(2019)
• Page Start: 2608
• Page End: 2616
• Publication Date: 2019-01-25
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c8nr08014c
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : It is revealed that the linear SCN − anion dictates critical restriction on the constituent ions of its derived 2D (PbX4 (SCN)2 ) framework. Abstract : Two-dimensional (2D) layered perovskites (A n +1 B n X3 n +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 I2 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 A2 Pb(SCN)2 X2 (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 (PbX4 (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. Cs2 Pb(SCN)2 I2 was revealed to possess improved stability and photo-response compared to (MA)2 Pb(SCN)2 I2 . Interestingly, Cs2 Pb(SCN)2 I2 and (MA)2 Pb(SCN)2 I2 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 Cs2 Pb(SCN)2 (I1− 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 Cs2 Pb(SCN)2 X2 perovskite system is a promising class of materials with good stability and color-tunability that deserves further exploration.