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

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 (δTPA). Perylene diimides (PDIs) are excellent n‐type organic semiconductor materials demonstrating distinguished thermal, optical, and chemical stability. Nonetheless, PDIs‐based scaffolds exhibit poor δTPA 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 δTPA of 3775 GM, which are among the highest values reported for PDIs excited in the NIR‐I region.