Fig. 4.

A plausible mechanism for ultralong phosphorescence in polymers. a The lifetime profiles of PSSNa in solid monitoring at 550 nm excited by 325 nm after exposed to air (humidity: 55%) for different periods of time. Inset shows the PXRD patterns of PSSNa in solid exposed for 0 and 3 h. b The excitation spectra of PSSNa polymer monitoring 440, 460, 480, 500, 520, 540, and 560 nm at 77 K. c 2D GI-WAXS pattern of dry PSSNa film. Optimized molecular structures of PSSNa models containing (d) two units and (e) six units by DFT. f Proposed mechanism for multicolor ultralong phosphorescence as the excitation wavelength changed. Noted that the schematic illustration of Model 1 and n represent the isolated and the aggregated chromophores in polymers, respectively