High-resolution mass spectra (HRMS) were recorded on a GCT premier CAB048 mass spectrometer operating in MALDI-TOF mode. Cyclic voltammograms were measured in a solution of tetra-n-butylammonium hexafluorophosphate (Bu4NPF6, 0.1 M) in dichloromethane or N,N-dimethylformamide containing the sample at a scan rate of 50 mV s -1 . Three-electrode system (Ag/Ag + , platinum wire and glassy carbon electrode as reference, counter and work electrode, respectively) was used in cyclic voltammetry measurement to determine HOMO energy levels (HOMO = -[Eox + 4.8] eV; LUMO = HOMO + Eg; Eox and Eg represent the onset oxidation potential relative to ferrocene and optical energy gap, respectively. The ground-state geometries were optimized using the density function theory (DFT) method with M06-2X functional at the basis set level of 6-31G (d,p). All the calculations were performed using Gaussian16 package. Photophysical property measurement UV-vis absorption spectra were measured on a Shimadzu UV-2600 spectrophotometer. PL spectra were recorded on a Horiba Fluoromax-4 spectrofluorometer. Fluorescence quantum yields were measured using a Hamamatsu absolute PL quantum yield spectrometer C11347 Quantaurus QY. Transient PL decay spectra were measured under nitrogen atmosphere (solution) or vacuum (neat film), using Quantaurus-Tau fluorescence lifetime measurement system (C11367-03, Hamamatsu Photonics Co., Japan). Circular dichroism (CD) spectra were recorded with a Chirascan spectrometer (Applied Photophysics, England). Circularly polarized photoluminescence (CP-PL) and circularly polarized electroluminescence (CP-EL) spectra were recorded at 100 nm min -1 scan speed with a commercialized instrument JASCO CPL-300 at room temperature.