Highly Conductive and Strongly Emissive Organic Semiconductor Single Crystals for Low‐Threshold Lasers and Bright Light‐Emitting Transistors

Abstract Organic semiconductor single crystals (OSSCs) exhibit long‐range intermolecular order and low defect density without grain boundaries, therefore leading to superior carrier transport than organic thin‐films but often weak emission due to aggregation‐caused quenching. Here, ultrathin 2D plate‐like OSSCs of an anthracene derivative, 4,4′ – bis ((E) ‐2‐ (anthracene‐2‐yl) vinyl) −1,1′ – biphenyl (BPVAn) are designed and synthesized, which exhibit not only strong emission with a photoluminescence quantum yield (PLQY) of 56% but also balanced and high charge carrier mobility of µ h = 5.6 cm 2 V −1 s −1 and µ e = 1.3 cm 2 V −1 s −1 for hole and electron transport, respectively. Organic light‐emitting transistors (OLETs) based on BPVAn OSSCs exhibit strong and spatially controllable light emission within both P‐ and N‐ conducting channels, with an external quantum efficiency (EQE) of up to 2.12% and a brightness of 1115 cd m −2 . In addition, OSSC parallelogram plates serve as whispering gallery mode (WGM) micro‐resonators and exhibit excellent laser characteristics, with a low threshold of 4.2 µJ cm −2 and a high quality (Q) factor of ≈1870 at an emission peak of 503 nm. These results indicate that OSSCs with excellent carrier transport, electroluminescence, and laser properties offer significant potential for the further development of electrically injected organic semiconductor lasers and optoelectronic devices.