Aggregation‐Induced Stimulated Emission of 100% Dye Microspheres

Abstract Dyes with aggregation‐induced emission (AIE) properties have gained interest due to their bright luminescence in solid‐state aggregates. While fluorescence from AIE dyes is widely exploited, relatively little is known about aggregation‐induced stimulated emission. Here, stimulated emission of tetraphenylethene (TPE)‐based organoboron AIE dyes, TPEQBN, in thin films and in microcavity lasers is investigated. Using femtosecond pump–probe spectroscopy, gain coefficients up to 230 cm⁻¹ at 500 nm are measured. Using rate equations, concentration‐ and pump‐dependent gain dynamics as well as laser build‐up dynamics are analyzed. During laser oscillation, radiative stimulated emission allows high instantaneous quantum yield greater than 90% to be achieved. Solid‐state microspheres made of 100% AIE dyes are fabricated via microfluidic emulsion and solvent evaporation method. Coupled with high gain and high refractive index of 1.76, microspheres as small as 2 µm in diameter show lasing by nanosecond pumping with a threshold of ≈10 pJ µm^–2. Polymer coated, but not bare, microspheres are internalized by live cells and generate narrowband cavity‐mode emission from within the cytoplasm. This work shows the potential of AIE dyes as laser materials.