Steric, conjugation and electronic impacts on the photoluminescence and electroluminescence properties of luminogens based on phosphindole oxide

Aggregation-induced emission (AIE) is currently receiving intense interest because of its important implications in photophysics. The structure-property relationship decipherment of AIE luminogens is of crucial importance for the fundamental understanding and application exploration. In this research, a series of novel luminogens based on phosphindole oxide (PIO), including a peculiar one with a folded conformation and apparent through-space conjugation, were synthesized and studied as models to elucidate the AIE mechanism. The significant impacts of steric, conjugation and electronic effects on the AIE property are presented based on the results of crystallography analysis, optical spectra measurements and theoretical computation. Non-doped yellow organic light-emitting diodes were fabricated with the new PIO-based luminogens, and they exhibited high brightness, good electroluminescence efficiencies and low efficiency roll-off.