Efficient Single-Phase Tunable Dual-Color Luminescence with High Quantum Yield Greater than 100% for Information Encryption and LED Applications

In modern society, the investigation of highly efficient photoluminescent bulk materials with excitation-induced tunable multicolor luminescence and multiexciton generation (MEG) is of great significance to information security and the application of optoelectronic devices. In this study, two bulk Cu-based halide crystals of (C4H10NO)4Cu2Br5·Br and (C4H10NO)4Cu2I5·I·H2O, respectively, with one-dimensional structures were grown by a solvent evaporation method. Unexpectedly, (C4H10NO)4Cu2I5·I·H2O displayed excitation-induced tunable dual-color luminescence; one band is a brilliant green-yellow emission centered at 547 nm with a high photoluminescence quantum yield (PLQY) of up to 169.67%, and the other is a red emission at 695 nm with a PLQY of 75.76%. Just as importantly, (C4H10NO)4Cu2Br5·Br exhibits a strong broadband green-yellow emission at 561 nm under broad band excitation ranging from 252 to 350 nm, a long PL decay lifetime of 106.9 μs, and an ultrahigh PLQY of 198.22%. These materials represent the first two examples of 1D bulk crystals and Cu(I)-based halides that have a PLQY exceeding 100%. Combining the unusual luminescence characteristics with theoretical calculations reveals that MEG contributes to the green-yellow emission with ultrahigh PLQY > 100%, and that the red emission can be ascribed to [Cu2I5]3– cluster-centered emission. Additionally, an information encryption method was designed based on the Morse Code. The high luminescence characteristics of LED devices fabricated using the (C4H10NO)4Cu2Br5·Br and (C4H10NO)4Cu2I5·I·H2O crystals appear to lead to promising applications in solid-state lighting. This work extends the catalog of high-performance luminescent materials and also promotes application prospects of low-dimensional copper-based halides in optoelectronics

(C₄H₁₀NO)PbX₃ (X = Cl, Br): Design of Two Lead Halide Perovskite Crystals with Moderate Nonlinear Optical Properties

Introducing electronegative species into organic constituents was considered to be one effective strategy for adjusting crystal symmetry and designing new nonlinear optical (NLO) materials. By substitution of C4 in piperidine (C5H11N) with electronegative oxygen, organic morpholine (C4H9NO) was easily obtained. Therefore, to design NLO crystals, we focused on combinations of stereochemically active lone-pair (SCALP) cation (Pb2+)-based chloride and bromide with morpholine molecules. In this work, two lead halide hybrid perovskite (C4H10NO)PbX3 (X = Cl, Br, abbreviated as MPbCl3 and MPbBr3, respectively) single crystals with moderate nonlinear optical properties were synthesized by a slow evaporation method. The two title crystals belong to orthorhombic space group P212121 with one-dimensional (1D) chainlike perovskite structures. Theoretical calculations revealed that the second harmonic generation (SHG) responses mainly originate from distorted {PbX6} octahedrons of the inorganic framework. Remarkably, moderate phase-matching SHG effects of about 0.70 and 0.81 times KH2PO4, large birefringences of 0.098 and 0.111 at 1064 nm, and large laser damage thresholds (LDTs) of 19.94 and 46.82 MW/cm2 were estimated for MPbCl3 and MPbBr3, respectively. This work provides a novel strategy for new purpose-designed hybrid NLO crystals by adjustment and modulation of chemical modification