S/Se-Annulated Star-Shaped Perylene Diimides (PDIs) with Large Two-Photon Absorption (TPA) Cross-Section in NIR-I Region

Graphical Two novel star-shaped fluorophores named PDI−S and PDI−Se are constructed by S/Se-fused perylene diimides (PDIs) connected with bicarbazole core. Particularly, PDI−S presents excellent two-photon absorption cross-action (δ TPA ) of 3775 GM excited with 800 nm light, which is the highest value based on PDIs motif in the NIR−I region (700–900 nm). Two-photon absorption (TPA) has attracted growing attention over recent years owing to the wide range of applications in organic nonlinear optical (NLO) materials. The quantitative sensitivity of a two-photon molecular entity is determined by its TPA cross-section (δ TPA ). Perylene diimides (PDIs) are excellent n-type organic semiconductor materials demonstrating distinguished thermal, optical, and chemical stability. Nonetheless, PDIs-based scaffolds exhibit poor δ TPA in the NIR−I region (700–900 nm) due to the lack of suitable molecular design. Here, two novel star-shaped PDIs fluorophores, namely PDI−S and PDI−Se, were constructed by four periphery S/Se-fused PDIs connected with bicarbazole core. PDI−S manifested excellent δ TPA of 3775 GM, which are among the highest values reported for PDIs excited in the NIR−I region.