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Stable, Color-Tunable 2D SCN-Based Perovskites: Revealing the Critical Influence of Asymmetric Pseudo-Halide on Constituent Ions
摘要： Two-dimensional (2D) layered perovskites (An+1BnX3n+1, n = 1, 2, …) have lately attracted significant research interest because of their enhanced ambient stability comparing to the conventional 3D counterparts. Beside the common A-site cation engineering, using an asymmetric pseudo-halide, SCN, anion in X-site anion has been recently proven as another effective approach to constitute 2D perovskite. Among them, 2D (MA)2Pb(SCN)2I2 was most widely investigated and honored as a promising material owing to its decent optoelectronic properties; however, its poor stability arouses concerns from the recent researches. In this study, a systematical composition engineering of A2Pb(SCN)2X2 (A= FA+, MA+, Cs+ and X= Br-, I-) was conducted. Our results revealed that linear SCN- anion may dictate critical restrictions on the constituent ions of its derived 2D framework (PbX4(SCN)2), which has not been extensively discussed yet. We demonstrated that using a smaller Cs+ cation can afford a more favorable 2D structure compared with the MA+ cation. Cs2Pb(SCN)2I2 was revealed to possess improved stability and photo-response compared to (MA)2Pb(SCN)2I2. Interestingly, Cs2Pb(SCN)2I2 and (MA)2Pb(SCN)2I2 seem to possess distinct electronic band structures as indicated by their discrepant photoluminescence spectra, for which the former exhibits a rather intense singlet emission at room temperature, as opposed to the latter having a dominant emission associated with triplet or defective states. Furthermore, using a smaller Cs+ cation also enables facile replacement of smaller halide anion. A series of mix-halide 2D Cs2Pb(SCN)2(I1-xBrx)2 (x = 0, 1/3, 1/2, 2/3, 1) with variant vivid color was explored by both calculation and experimental efforts to corroborate the further enhanced stability when x value increases. The results revealed in this work might be inherent trait of 2D SCN-based perovskites and also unveil that all inorganic 2D Cs2Pb(SCN)2X2 perovskite system is a promising class of material with decent stability and color-tunability, deserving further explorations.
关键词： stability,Cs cation,pseudo-halide,SCN- anion,color-tunability,2D perovskite
更新于2025-11-14 17:04:02
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Two-dimensional Ruddlesdena??Popper layered perovskite for light-emitting diodes
摘要： Solution-processed metal halide perovskite light-emitting diodes (PeLEDs) have attracted extensive attention due to the great potential application in energy-efficient lighting and displays. Two-dimensional Ruddlesden–Popper (2DRP) layered perovskites exhibit high photoluminescence quantum efficiency, improved film morphology, and enhanced operational stability over their three-dimensional counterparts, making them attractive for high-performance PeLEDs. In addition, 2DRP perovskite materials with a tunable exciton binding energy are suitable for preparing PeLEDs with color-tunability. In this perspective, we first introduce the merits of the 2DRP layered perovskites in terms of their structural characteristics. The progress in 2DRP PeLEDs is then reviewed. The challenges and new opportunities of the PeLEDs are finally discussed. We hope to open up new perspectives for rational designs of the 2DRP perovskite materials for PeLEDs with unprecedented efficiency and stability.
关键词： operational stability,film morphology,photoluminescence quantum efficiency,Two-dimensional Ruddlesden–Popper layered perovskite,color-tunability,light-emitting diodes
更新于2025-09-19 17:13:59
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Towards white light emission from a hybrid thin film of a self-assembled ternary samarium( <scp>iii</scp> ) complex
摘要： A new samarium complex [Sm(hfaa)3(Py-Im)] (ML) was synthesized by utilizing hexafluoroacetylacetone (hfaa) and 2-(2-pyridyl)benzimidazole (Py-Im) as coordinating ligands. A single crystal X-ray analysis shows that in the solid-state the complex dimerizes through intermolecular hydrogen-bonding with N–H···O (2.127 ?) and N–H···F (2.576 ?) interactions. The complex in the solid-state displayed highly monochromatic brilliant red emission with Commission International de I’Eclairage (CIE) color coordinates of 0.6532; 0.3336, with a remarkably long luminescence lifetime (≈ 204.47 ± 4.043 μs) and a high intrinsic quantum yield (≈ 6.60 %). Furthermore, the complex in different organic media displayed color tunability from orange (CIE; 0.6071; 0.3568) to violet (CIE; 0.3634; 0.2144) with from 105.50 ± 0.143 – 14.27 ± 0.033 μs. Hybrid and flexible thin films obtained by doping different concentrations (1%, 2%, 4% and 6%) of the complex into the poly(urethane) (PU) polymer matrix also exhibited color tunability from violet (CIE; 0.3380; 0.2162) to light orange (CIE; 0.5666; 0.3408). White light emission from a 1% doped thin film of the complex was realized by changing the excitation wavelength. The new material could be a potential candidate for the fabrication of full-color display devices and for solid-state lighting (SSL) applications.
关键词： luminescence,white light emission,color tunability,samarium complex,solid-state lighting
更新于2025-09-19 17:13:59
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Novel multi-wavelength excitable single-component phosphor system for application in white-LEDs
摘要： A novel color-tunable phosphor of BaZnO2:xEu3+ (x=0 to 20 mol%) has been sucessfully prepared via high-temperature calcination method using alkaline earth metal as the charge compensator. Uncommonly, BaZnO2:Eu3+ is a multi-wavelength excitable phosphor due to its wide absorption spectrum ranging 250-550 nm. It shows broad white (400-700 nm), orange (~580 nm) and red (~611 nm) photoluminescence (PL) under 370 nm, 395 nm and 467 nm excitations, respectively and were assigned to one or more 5D0→7FJ (J =1 to 4) transitions of Eu3+ ion. An efficient energy transfer between Zn2+ and Eu3+ has been observed upon systematically increasing the concentration of Eu3+ ion. Scanning Electron Microscopy images indicated elongated rod-like structures with an average diameter of ~20 nm. The chromaticity coordinates (x, y) were found to be positioned at white (0.33, 0.42), orange (0.51, 0.42) and red (0.65, 0.34) regions correspond to 370 nm, 395 nm and 467 nm excitations, respectively. The temperature-dependent luminescence spectrum of BaZnO2:Eu3+ under the excitation of 467 nm was also studied. It exhibited good thermal stability and a marginal drop in photoluminescence intensity by 4.29% at 150oC was observed. The mathematical calculation of the activation energy was approximately 0.20 eV. The results indicate the suitability of the phosphor for LEDs applications, which is otherwise difficult to obtain in single-component system.
关键词： white LEDs,Phosphor,color tunability,photoluminescence
更新于2025-09-16 10:30:52
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Highly Efficient and High Peak Transmittance Colorful Semitransparent Organic Solar Cells with Hybrid-Electrode-Mirror Microcavity Structure
摘要： Microcavity is an efficient approach to manufacture colorful semitransparent organic solar cells (ST-OSCs) with high color purity by tailoring the transmission spectrum to narrow peaks. However, in this type of colorful semitransparent devices, high power conversion efficiency (PCE) and high peak transmittance are not yet simultaneously achieved. This paper proposes a new type of microcavity structure to achieve colorful ST-OSCs with both high PCE and high peak transmittance, in which hybrid Au/Ag electrode is used as mirror and WO3 as spacer layer. Firstly, it is demonstrated that the hybrid Au/Ag electrode mirror brings about an improvement of 7.7% and 5.5% for PCE and peak transmittance respectively, when compared with those of the reference devices using Ag electrode mirror. Specifically, the PCE of the optimized devices reaches the satisfactory value of over 9%, and the peak transmittance is over 25%. This value of PCE is the highest one reported so far for the microcavity-based ST-OSCs with the same peak transmittance. Secondly, it is demonstrated that the second-order resonance of the microcavity can be used to improve the color purity of green ST-OSCs by narrowing the transmission peak and the combination of the second-order and third-order resonance can be used to construct colorful ST-OSCs with mixed colors. Thus, a novel approach is developed to tune the color of ST-OSCs, which is based on high-order resonance modes of the microcavity.
关键词： transparency,color mixing,color tunability,semitransparent organic solar cells,interface optimization,hybrid Au/Ag electrode,microcavity,efficiency
更新于2025-09-12 10:27:22
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Photoluminescent and structural properties of color tunable trivalent europium doped SrGdAlO4 nanophosphors
摘要： A series of Eu3+ ion doped SrGdAlO4 nanophosphors were prepared via solution combustion technique utilizing urea as a fuel. Structural properties of the tetragonal phase of the host/doped lattice belonging to the space group I4/mmm were characterized by powder X-ray diffraction (PXRD). Photoluminescence spectra, decay curves, UV–Visible diffuse reflectance spectra (UV–Vis DRS) and Judd–Ofelt analysis were utilized to characterize the photoluminescent properties. The radiative rates (Ar), branching ratios (Br) and intensity parameters (?λ) were estimated by Judd–Ofelt analysis. The optimal doping concentration of europium ions for SrGdAlO4 host lattice was found to be 20 mol%, above which concentration quenching was observed due to dipole–dipole interactions. CIE coordinates values lie in the blue region at lower concentrations of Eu3+ ions, which shifted towards white and then to reddish-orange region with higher concentrations of Eu3+ ions, suggesting the color tunable property of the synthesized nanophosphors. Lower value of CCT and color tunable phenomenon proved it as potential candidate for warm white light and phosphor converted white light emitting diodes (Pc-WLEDs) applications. The optical band gap of both host lattice (5.50 eV) as well as of 20 mol% Eu3+ doped SrGdAlO4 nanophosphors (5.26 eV) lie in the range of semiconductors which enhanced their areas of applications.
关键词： Nanophosphors,Color tunability,Solution combustion,Photoluminescence,Judd–Ofelt analysis,Semiconductor
更新于2025-09-09 09:28:46