Highly Efficient Organic Afterglow from 2D Layered Lead-Free Metal Halide in Both Crystals and Thin Films under Air Atmosphere.

Organic afterglow materials (OAMs) with lifetime longer than 0.1 s have recently received much attention for their fascinating properties meeting the critical requirements of applications in newly-emerged technologies. However, the development of OAMs lags behind for their low luminescent efficiency. Usually, enhancing the phosphorescence efficiency of organic materials causes a short lifetime. Here, we report two kinds of OAMs, 2D layered organic-inorganic hybrid Zinc bromides (PEZB-NT and PEZB-BP), obtained in an environmentally friendly ethanol solvent by low-temperature solution method. They display highly efficient and persistent luminescence at air in both crystals and thin films with phosphorescent quantum yield up to 42% in crystals, and 27% in film. For OAMs, the two quantum yields are the highest values ever reported for crystals and films, respectively. Due to the excellent crystalline and film-forming ability, PEZB-NT and PEZB-BP in ethanol can be used as ink to construct patterns in various rigid and flexible substrates, including paper, iron, plastic, marble, tin foil and cloth. Consequently, the novel OAMs show great application prospects in the field of anti-counterfeiting and information storage for economic synthesis, solution processing, and easy operation.