Short-wavelength infrared (SWIR, 1000–3000 nm) light detection underpins a wide range of applications, including non-invasive medical imaging, autonomous navigation, and secure optical communications. Commercial SWIR photodetectors based on InGaAs and other III–V semiconductors offer excellent performance, but their complex epitaxial growth, high cost, and mechanical rigidity hinder large-scale deployment and flexible integration. In contrast, organic photodetectors (OPDs) can be solution-processed from tunable molecular semiconductors, providing advantages such as low cost, spectral tailorability, and mechanical flexibility. Nevertheless, achieving efficient SWIR photoresponse with organic materials remains a long-standing challenge.
Researchers led by Prof. Jun Liu from the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, report a breakthrough molecular design that overcomes this limitation. Their new molecule, named NBN-4, employs meta -dicyanophenyl end groups to induce J -aggregation in a thiophene-fused BODIPY tetramer featuring resonant N—B←N bonds—a cooperative molecular packing behavior that extends light absorption to longer wavelengths.
This subtle but powerful modification enhances the local dipole moment and strengthens intermolecular electrostatic interactions, resulting in a strong redshift in absorption to 1205 nm. The resulting organic photodetectors achieve a peak responsivity of 0.15 A W⁻ 1 and a specific detectivity of 4.78×10 11 Jones at 1200 nm—ranking among the best reported for SWIR OPDs.
Computational and spectroscopic analyses reveal that the increased local dipole moment (7.64 Debye) in NBN-4 facilitates tight molecular packing and efficient charge separation. Ultrafast transient absorption spectroscopy further confirms faster exciton dissociation and hole transfer dynamics in the NBN-4 blend. Combined with improved charge balance and reduced recombination, these factors enable superior photodetection performance.
“Our study demonstrates that precisely engineered oligomer frameworks and tailored end-group chemistry can promote J -aggregation, effectively broadening the optical response of organic semiconductors.” said Prof. Liu. “This cyanation-driven J -aggregation approach provides a general strategy for designing next-generation organic semiconductors for SWIR detection and beyond.”
The study opens new opportunities for developing flexible, lightweight, and cost-effective infrared sensors suitable for wearable electronics, biomedical monitoring, and artificial vision systems.
Science Bulletin
Experimental study