Star-shaped triazine-cored ladder-type ter(p-phenylene)s for high-performance multiphoton absorption and amplified spontaneous blue emission

Lacking high-performance blue emissive multiphoton absorption (MPA) materials particularly for frequency up-converted amplified spontaneous emission (ASE) or lasing hampers novel breakthroughs in a wide-range of laser-based applications. Besides, it is fundamentally challenging to develop highly efficient organic multiphoton-pumped ASE or lasing materials because of intrinsically weak MPA responses restricted by limited and inefficient intramolecular π-electron delocalization. Despite such short π-conjugated ter(p-phenylene) backbones, newly developed star-shaped triazine-cored ladder-type ter(p-phenylene)s exhibit not only remarkably strong multiphoton (from two- to five-photon) induced photoluminescence but also highly efficient MPA properties including a record high intrinsic 2PA cross-section of 5120 GM and outstandingly large intrinsic 3PA cross-section of 3.3 × 10^-76 cm⁶ s² at 1200 nm for a blue emissive fluorophore as well as highly efficient 2PA pumped blue ASE with efficiency up to ∼1.0%, in sharp contrast to triarylamine-based star-shaped analogues. As a result, TA(TL)-Ph(3)-CBZ is a highly efficient blue emissive MPA material for practical MPA applications. The synergy of the triazine core and the end-groups in this multidimensional structural framework proved indispensable to such a high-performance MPA response.