ABSTRACT
Organic-inorganic hybrid metal halides have unique optical and electronic properties, which are advantageous in the study of nonlinear optical materials. To investigate the effect of stereoactive lone pair electrons and the induction of organic cations on the structure of hybrid antimony(III) halides on nonlinear optics, we synthesize two noncentrosymmetric hybrid antimony(III)-based halide single crystals (TMA)3Sb2X9 (TMA = NH(CH3)3+, X = Cl, Br) by a room-temperature slow evaporation method, and their single-crystal structures, phase transition, X-ray photoelectron spectroscopy, and energy-band structure calculations are studied. More importantly, second-harmonic generation results of (TMA)3Sb2X9 (X = Cl, Br) are about 0.7 and 0.8 × KH2PO4(KDP), respectively. Interestingly, (TMA)3Sb2Cl9 single crystals undergo a reversible structural transition from Pc (No. 7) at room temperature to P21/c (No. 14) at 400 K, while the (TMA)3Sb2Br9 single crystals belong to the noncentrosymmetric space group R3c (No. 161), which clarifies the previous results. This work not only deepens the understanding of the role in lone pair electrons and organic cations in the structural induction in antimony-based halide perovskite materials but also provides guidance for subsequent nonlinear optical explorations.
ABSTRACT
Mn(II)-based hybrid halides have attracted great attention from the optoelectronic fields due to their nontoxicity, special luminescent properties, and structural diversity. Here, two novel organic-inorganic hybrid Mn(II)-based halide single crystals (1-mpip)MnCl4·3H2O and (1-mpip)2MnCl6 (1-mpip = 1-methylpiperazinium, C5H14N2+) were grown by a slow evaporation method in ambient atmosphere. Interestingly, (1-mpip)2MnCl6 single crystals exhibit the green emission with a PL peak at 522 nm and photoluminescence quantum yields (PLQYs) of ≈5.4%, whereas (1-mpip)MnCl4·3H2O single crystals exhibit no emission characteristics. More importantly, there exists a thermal-induced phase transformation from (1-mpip)MnCl4·3H2O to emissive (1-mpip)2MnCl6 at 372 K. Moreover, a reversible luminescent conversion between (1-mpip)MnCl4·3H2O and (1-mpip)2MnCl6 was simply achieved when heated to 383 K and placed in a humid environment or sprayed with water. This work not only deepens the understanding of the thermal-induced phase transformation and humidity-sensitive luminescent conversion of hybrid Mn(II)-based halides, but also provides a guidance for thermal and humidity sensing and anticounterfeiting applications of these hybrid materials.
ABSTRACT
Lead (Pb)-free halide hybrid materials have received a great deal of attention because of their potential in optoelectronic applications. However, heteroatom-based amine lead-free tin halide hybrid single crystals have not been well investigated yet. Detailed synthetic processes, growth, crystal structures, and stability of (ACH2CH2NH3)2SnBr6 (A = OH or SH) and (BCH2CH2NH3)2SnI4 (B = I or SH) single crystals were investigated. Interestingly, (IH3NCH2CH2SSCH2CH2NH3)2HPO3 exhibited orange-red photoluminescence (PL) at about 620 nm with an average PL lifetime of about 912 ns. (HSCH2CH2NH3)2SnI4 single crystals exhibited a PL peak at 620 nm with an average PL lifetime of about 0.607 ns. More importantly, (HSCH2CH2NH3)2SnI4 single crystals exhibited reversible red-black color transformations when exposed to a H3PO2 solution and an ambient atmosphere, which was attributed to oxidation from Sn2+ to Sn4+, rather than from I- to I3- (I2). The intriguing characteristics should provide guidance for further optoelectronic applications of these Pb-free halide hybrid materials.
ABSTRACT
Light-emitting diodes (LEDs) with the circularly polarized luminescence features have attracted attention to the promising applications ranging from solid-state lighting and displays to bioencoding and anticounterfeiting. The prerequisite of circularly polarized luminescence is highly emissive chiral materials. Here, we demonstrated that (R/S-MBA)4Cu4I8·2H2O (MBA = α-methylbenzylaminium) and acentric Gua6Cu4I10 (Gua = guanidinium) single crystals were grown on the basis of Gua3Cu2I5 by the slow evaporation method. (R/S-MBA)4Cu4I8·2H2O single crystals exhibited excellent circularly polarized luminescence (CPL) characteristics. More importantly, ultraviolet-pumped LEDs (UV-LEDs) based on (R/S-MBA)4Cu4I8·2H2O and Gua6Cu4I10 single crystals exhibit a higher optical selectivity when exposed to right-handed and left-handed circular polarization (RCP and LCP) conditions. (S-MBA)4Cu4I8·2H2O single crystals and Gua6Cu4I10 single crystals induced by the (R)-MBA cation exhibit the different polarized light intensities at PL peak positions in different λ/4 waveplate polarizer angle directions, which provides new possibilities for the further applications from 3D displays to spintronics, as well as anticounterfeiting.
