Fast and efficient room-temperature phosphorescence from metal-free organic molecular liquids

Liquid is the most flexible state of condensed mater and shows promise as a functional soft material. However, these same characteristics make it challenging to achieve efficient room-temperature phosphorescence (RTP) from metal-free organic molecular liquids. Herein, we report efficient RTP from liquefied thienyl diketones bearing one or two dimethyloctylsilyl (DMOS) substituents. These solvent-free liquids exhibit high RTP quantum yields up to 5.6% in air and 25.6% under Ar due to their large RTP rate constant exceeding 5,000 s–1. Introducing two DMOS substituents sufficiently suppresses aggregation-caused quenching of the molecularly emissive phosphors, demonstrating a design principle for RTP-active liquid materials.