Long persistent luminescence (LPL) materials have a wide range of applications, such as in architectural decorations, safety signs, watch dials, and glow-in-the-dark toys. Present LPL materials based on inorganics must be processed into powders and blended with polymer matrices before use. However, micro powders of inorganic LPL materials show poor compatibility with common polymers, limiting the mechanical properties and transparency of the composites. Here, we report a polymer-based organic LPL (OLPL) system that is flexible, transparent, and solution-processable.Following low-power excitation at room temperature, this polymer-based OLPL system exhibits LPL after phosphorescence from the donor.Long persistent luminescence (LPL), also called long afterglow, is the phenomenon when, after being excited, a material in the dark emits light for several seconds, minutes, hours, or even days. [1] Received: ((will be filled in by the editorial staff))Revised: ((will be filled in by the editorial staff))