Deep-Blue Organic Single-Crystal Emitter Enabling a Low-Threshold Laser and Light-Emitting Transistor

π-conjugated organic small molecules offer an efficient route to deep blue emission but often hinder carrier transport properties. Organic single crystals, characterized by their highly ordered packing structure, present a promising solution for both efficient luminescence and enhanced carrier mobility. In this work, we designed and synthesized a novel organic small molecule (BCS) and prepared its single crystals. The BCS single crystals exhibit bright deep blue emission with a high solid-state photoluminescent efficiency of 51% and carrier mobility of 0.18 cm2·V–1·s–1 because the significant twisted structures of BCS molecules in the crystals weaken π-π interaction and facilitate carrier transport. The regular morphology of these crystals provides a high-quality resonator, enabling superior lasing emission with a low threshold of 10.32 μJ·cm–2. Further, we developed BCS crystal-based organic light emitting transistors and achieved excellent deep blue electroluminescence with CIE coordinates of (0.16, 0.08). This work opens a new avenue for the design of deep blue emitters based on π-conjugated organic small molecules, advancing the development of superior optoelectronic materials and wide color gamut displays.