Photostability Enhancement in Solution-Processable Organic Laser Materials: A Fluorination-Based Strategy

Organic semiconductor materials offer considerable advantages in flexibility, processability, and wavelength tunability. Particularly solution processability stands out by significantly reducing the fabrication cost and complexity of organic semiconductor lasers. However, solution-processable organic laser gain media currently face critical challenges, including optical gain loss from molecular aggregation, difficult-to-control thin-film morphology, and inherent deficiencies in the thermal and optical stability of organic materials. To overcome these issues, this work employs a fluorination strategy to modify BSFCz, the first solution-processable organic laser gain material capable of supporting long-pulse excitation, yielding two new materials with significantly enhanced photostability. Systematic structure-performance relationship investigations demonstrate that the introduction of fluorine substituents effectively reduces the HOMO and LUMO energy levels of the materials, while strengthening the non-π-π stacking intermolecular interactions in the aggregated state. These changes allow the newly developed materials to retain high luminescence efficiency while achieving significantly enhanced stability. The optimized candidate, 3,5-diF-BSFCz, exhibits a high photoluminescence quantum yield of 76% and a low amplified spontaneous emission (ASE) threshold of 1.36 μJ cm^-2 when dispersed in the CBP host. The doped film retains 80% of its initial emission intensity after 10,000 consecutive excitation pulses at twice the ASE threshold, demonstrating a 4.5-fold enhancement in optical stability over nonfluorinated BSFCz. This work not only presents a high-performance, solution-processable organic laser gain medium, but also experimentally validates the fluorination strategy as an effective molecular engineering approach for performance optimization, thereby providing a rational design pathway toward efficient organic laser materials.