Regulating photoluminescence through single-crystal-to-single-crystal transformation of solvent-containing zero-dimensional hybrid metal halide isomers

Abstract

Regulating photoluminescence (PL) properties induced by single-crystal-to-single-crystal (SCSC) transformation has sparked significant interest in the research of zero-dimensional organic–inorganic metal halides (0-D OIMHs). To best of our knowledge, the SCSC transformation of solvent-containing 0-D OIMH isomers hasn’t been reported yet. In this work, we report the first example of SCSC transformation between two isomers containing lattice solvent molecules, namely α- and β-[EtPPh3]2[SbCl5]·MeCN (α- and β-1·MeCN; EtPPh3 = ethyltriphenylphosphonium; MeCN = acetonitrile). Differential scanning calorimetry (DSC) results show that the SCSC transformation from α- to β-1·MeCN is an exothermic process, implying that β-1·MeCN is a more stable phase than α-1·MeCN. Moreover, α- and β-1·MeCN exhibit bright orange (emission peak: 610 nm) and red (emission peak: 635 nm) emission under 360/365 nm excitation, respectively. DFT calculations suggest that the negligible self-absorption and a strong exciton confinement contribute to their effective PL emission. By analyzing temperature-dependent PL spectra, β-1·MeCN has been found to exhibit stronger electron-phonon coupling under excitation than α-1·MeCN. Thus, the broader emission with full width at half maximum (FWHM: 134 vs. 147 nm) and the higher photoluminescence quantum yield (PLQY: 40.37% vs. 70.50%) have been realized by SCSC transformation from α- to β-1·MeCN by heating at 92 °C. Benefitting from the regulation of PL performances brought by SCSC transformation, the white light-emitting-diode (LED) devices assembled by using β-1·MeCN as red phosphor could be optimized, and the CRI reaches as high as 95.3.