Persistent room temperature phosphorescence films based on star-shaped organic emitters

Developing pure organic materials with ultralong lifetimes in neat film is attractive but challenging. Here, we report a series of metal-free star-shaped organic luminogens (CzO, CzS and CzSe) based on carbazole and chalcogen atoms (O, S and Se), which exhibit persistent phosphorescence in neat film at room temperature. Specifically, CzS containing sulfur atoms achieves excellent comprehensive performance with a phosphorescence lifetime of 356 ms and a phosphorescence quantum yield of 5.0% in its neat film, which can be observed even under ambient conditions with a lifetime of 166 ms. Due to its persistent phosphorescence performance, the CzS neat film can be potentially used in the field of information encryption. Moreover, CzS exhibits white electroluminescence from its dual emission of fluorescence and phosphorescence.