Large-Size crystal based on rare earth-free Cu(I) hybrid trigger yellow light with high emissive quantum yields

Phase Transition and Luminescent Property Change Induced by Different Organic Cations in One-Dimensional Double Perovskites

Double perovskites (DPs) have attracted attention in the field of luminescence due to their inherent broadband emission of self-trapping excitons. In this work, we choose [(CH3)3NCH2CHCH2]+ and [CH3CHOHCH2NH2]+ as organic cations to synthesize two new organic-inorganic hybrid DPs, [(CH3)3NCH2CHCH2]2KInCl6 (1) and [CH3CHOHCH2NH2]2KInCl6 (2). The [KCl6]3- and [InCl6]3- octahedra are interchangeably connected by sharing two opposite faces, forming a one-dimensional coordination chain. Each K atom coordinates with six chlorine atoms in 1, while it coordinates with two oxygen atoms in addition to the six chlorine atoms in 2. The coordination between ions K and O in compound 2 may have significantly reduced its luminescence. As a result, compound 1 shows bright-yellow light with a quantum yield of more than 90%, while 2 shows weak blue light with a quantum yield of only 0.98%. In addition, different from no phase transition found in 2, 1 undergoes a reversible phase transition at 324/307 K in the heating-cooling cycle. Through structural and spectral analysis and density functional theory calculation, we conclude that the larger degree of [InCl6]3- octahedral distortion and the larger anion distance (In···In) also cause the PLQY of compound 1 to be higher than that of compound 2.

Dual-Emissive γ-[Cu4I8]4- Enables Luminescent Thermochromism in an Organic-Inorganic Hybrid Copper(I) Halide

A highly luminescent (C13H28N2)2Cu4I8 single crystal containing isolated γ-[Cu4I8]4- anionic cluster was synthesized without the use of unsaturated cations. To the best of our knowledge, compounds bearing such like anions are not dual-emitting under UV excitation. However, dual emission does occur in (C13H28N2)2Cu4I8. Moreover, the emission bands were found to be temperature-sensitive, allowing tuning of the emission colors from blue (0.19, 0.20) to green (0.33, 0.47) in the Commission International de L' Eclairage (CIE) chromaticity coordinates. Remarkably, the color could be restored on returning to the initial temperature, confirming an efficient and reversible luminescent thermochromic effect in (C13H28N2)2Cu4I8. The origin of this excellent optical performance is discussed, and the difference in the mechanism with the dual-emissive Cu(I) halide complexes is also elucidated. Overall, our work provides a promising way to achieve efficient luminescent thermochromism. The developed (C13H28N2)2Cu4I8 represents one of the viable alternatives for eco-friendly luminescent thermochromic materials.