High-efficiency color-tunable ultralong room-temperature phosphorescence from organic–inorganic metal halides via synergistic inter/intramolecular interactions

Materials exhibiting highly efficient, ultralong and multicolor-tunable room-temperature phosphorescence (RTP) are of practical importance for emerging applications. However, these are still very scarce and remain a formidable challenge. Herein, using precise structure design, several novel organic–inorganic metal-halide hybrids with efficient and ultralong RTP have been developed based on an identical organic cation (A). The original organic salt (ACl) exhibits red RTP properties with low phosphorescence efficiency. However, after embedding metals into the organic salt, the changed crystal structure endows the resultant metal–halide hybrids with excellent RTP properties. In particular, A2ZnCl4·H2O exhibits the highest RTP efficiency of up to 56.56% with a long lifetime of up to 159 ms. It is found that multiple inter/intramolecular interactions and the strong heavy-atom effect of the rigid metal–halide hybrids can suppress molecular motion and promote the ISC process, resulting in highly stable and localized triplet excitons followed by highly efficient RTP. More crucially, multicolor-tunable fluorescence and RTP achieved by tuning the metal and halogen endow these materials with wide application prospects in the fields of multilevel information encryption and dynamic optical data storage. The findings promote the development of phosphorescent metal-halide hybrids for potential high-tech applications.

Aminoacetophenone (200 ul) were dissolved in 1 mL HX (X = Cl and Br) at 100 °C with constant stirring for 10 min to form a clear solution.Then, crystals were obtained by slow cooling to room temperature and finally dried at 45 °C in an oven.
Structure (or Chemical Component) Characterizations: Single-crystal X-ray diffraction data were collected from Agilent Technologies Gemini AUltra system with Mo-Kα radiation (λ = 0.71073 Å) at RT.The structures were resolved and refined using direct methods with OLEX2.Powder X-ray diffraction (PXRD) and d were performed on an X-ray powder diffractometer (D2 Phaser, Bruker, Germany) at RT.A typical scan rate was 10 s step -1 with a step size of 0.02°.Thermogravimetry analysis (TGA) was carried out using a TA instrument (Q50 TGA system).The samples were heated from RT (~ 25 °C) to 800 °C with at a rate of 10 °C min -1 under an argon flux of 20 mL min -1 .XPS measurements of the samples were conducted on a Thermal K-Alpha spectrometer equipped with a monochromatic Al Kα X-ray source.Parameters of the π-π interactions and hydrogen-bond geometry in A2ZnCl4•H2O, A2ZnBr4•H2O, A2SnCl6, A2H3OInCl6•H2O, ACl and ABr got from OLEX2.
Optical Characterizations: UV-visible absorption spectra of the materials were obtained from the Agilent Cary5000 spectrophotometer equipped with integrating sphere to exclude signal due to light scattering.BaSO4 was used as a non-absorbing reflectance reference for diffuse-reflectance measurements.The photoluminescence quantum yields were measured on a calibrated integrating sphere.Steady-state RT and temperature-dependent excitation and emission spectra were recorded on a photoluminescence spectrometer (Horiba Fluorolog-3, Horiba Ltd.), and their corresponding transient photoluminescence spectra were also recorded on Fluorolog-3 with the time-correlated single-photon counting (TCSPC) mode.The photoluminescence quantum yields (PLQY) were measured on Fluorolog-3 with a calibrated integrating sphere.Time-resolved emission spectroscopy (TRES) characterization were performed on FLS 1000.In detail, a pulsed light source excites a sample, and the resulting photoluminescence attenuation is continuously recorded as a function of the emission wavelength to create a three-dimensional data that includes photoluminescence spectra and time correlation.The FluOracle software of FLS 1000 can automatically obtain TRES spectra using TCSPC or MCS modes to measure short and long lifetimes, respectively.VPLED310 is set to a pulse width of 800 ms and 10 Hz repetition rate.Use MCS mode to obtain photoluminescence attenuation in the wavelength range of 400-700 nm with a step size of 5 nm.Fourier transform infrared spectroscopy (FTIR) was measured by the Perkin Elmer (United States), using a DTGS detector.The parameter settings: scanning range: 4000~400 cm -1 , resolution: 4 cm -1 , cumulative scanning of 4 ATR tests.Spectral analysis using the instrument's built-in Spectrum software.
Femtosecond Transient Absorption Spectroscopy Measurements: The fs-TA measurements were performed on a Helios pump-probe system (Ultrafast Systems LLC) combined with an amplified femtosecond laser system (Coherent).Optical parametric amplifier (TOPAS-800-fs) provided a 330 nm pump pulse (~ 0.5μJ/pulse, which was excited by a Ti: sapphire regenerative amplifier (Legend Elite-1K-HE; 800 nm), 35 fs, 7 mJ/pulse, 1 kHz) and seeded with a mode-locked Ti: sapphire laser system (Micra 5) and an Nd: YLF laser (EvolutIon 30) pumped.Focusing the 800 nm beams (split from the regenerative amplifier with a tiny portion, ~ 400 nJ/pulse onto a CaF2 plate produced the white-light continuum (WLC) probe pulses (350-650nm).
The pulse-to-pulse fluctuation of the WLC is corrected by a reference beam split from WLC.A motorized optical delay line was used to change the time delays (0 ~ 8 ns) between the pump and probe pulses.The instrument response function (IRF) was determined to be ~ 100 fs by a routine cross-correlation procedure.The instrument response function (IRF) was determined to be ~100 fs by a routine cross-correlation procedure.A mechanical chopper operated at a frequency of 500 Hz used to modulate the pump pulses such that the fs-TA spectra with and without the pump pulses can be recorded alternately.
Hirshfeld Surfaces and Two-Dimensional Fingerprint Plots: The intermolecular interactions for all materials in this work were investigated through Hirshfeld surface analysis by using Crystal Explore 17.5.1 First, the CIF file was uploaded into the software.In the window of surface generation, the surface was set as "Hirshfeld", and the option "None" was chose for its property.After generating a Hirshfeld surface, "Surface property" was set as "dnorm".Further, in the window of two-dimensional fingerprint plots, the option "di vs de" was defaulted for the type.dnorm is the normalized contact distance, di is the distance from a point on the Hirshfeld surface to the nearest atom inside the surface, and de is the distance from a point on the Hirshfeld surface to the nearest atom outside the surface.
Computational Methods: All calculations were based on the density functional theory (DFT) implemented in the VASP code.The projector augmented wave (PAW) method was used with a cutoff energy of 400 eV.The electron exchange correlation effect was represented by the PerdewBurke-Ernzerhof (PBE) functional under the generalized gradient approximation (GGA).The optimization of lattice parameters was based on the experimentally measured values, while the atomic positions were optimized until the force on each atom was <0.02 eV Å -1 .The total energy was converged to 10 -6 eV.The k-point separation was set as 0.04 Å -1 in the Brillouin zone leading to corresponding Γ-centered k-point meshes of A2ZnBr4•H2O: 3×1×1; A2SnCl6: 3× 2 × 2; ACl: 5×2×2; A2H3OInCl6•H2O: 3×3×1.

Figure S1 .
Figure S1.Schematic illustration of the strategies used to construct high-efficiency RTP system in this work.

Figure S7 .
Figure S7.Transient RTP decay curve of ACl, recorded at 610 nm at 80 and 280 K.

Figure S11 .
Figure S11.The TRES spectra of (a) A2ZnCl4•H2O and (b) ACl, recorded at RT.For the TRES test, a pulsed light source is first used to excite the sample, then the resulting PL attenuation is continuously recorded as a function of the emission wavelength to create a three-dimensional data that includes photoluminescence spectra and time correlation.

Figure S16 .
Figure S16.The Hirshfield surface analyses of ACl.Image showing the Hirshfeld surface of ACl.The Hirshfeld surface is constituted by a series of iso-surfaces consisting of red, white, and blue regions.Red means the intermolecular contact distance is shorter than the van der Waals distance, white means equal and blue means longer.(Two-dimensional fingerprints and relative contributions (in %) to different Hirshfield surface areas of intermolecular contacts in ACl.)

Figure S21 .
Figure S21.Schematic illustration of the centroid-centroid distances and dihedral angle between two adjacent phenyl rings for (a) ACl and (b) ABr.

Figure S23 .
Figure S23.The electron distribution profiles calculated by the DFT-PBE method of (a) VBM and (b) CBM for ACl along a axis.

Figure S24 .
Figure S24.The electron distribution profiles calculated by the DFT-PBE method of (a) VBM and (b) CBM for A2H3OInCl6•H2O along a axis.

Figure S25 .
Figure S25.The electron distribution profiles calculated by the DFT-PBE method of (a) VBM and (b) CBM for A2SnCl6 along a axis.

Figure S26 .
Figure S26.The electron distribution profiles calculated by the DFT-PBE method of (a) VBM and (b) CBM for A2ZnCl4•H2O along a axis.

Figure S29 .
Figure S29.(a) Crystal structure of A2ZnBr4•H2O view along the a axis.(b-d) Crystal structure of ABr viewed along different directions.

Figure S31 .c
Figure S31.(a) Prompt and delayed spectra of ABr.(b) Transient PL decay curves of ABr, measured at RT. (c) Temperature-dependent delayed spectra of ABr.