Breaking the 1250 nm Barrier: A Computational Approach to Light Upconversion via Triplet–Triplet Annihilation in the Silica Telecom Band

The 1250-1675 nm region is the spectral range exploited in modern telecommunications and quantum networks because of the high transparency of silica-based nanofibers. Nevertheless, the low efficiency of detectors and sensors in that region requires light upconversion (UC). This is achieved with inorganic dopants, often based on rare-earth elements or metal nanoparticles that are characterized by a low chemical flexibility besides sustainability issues. Triplet-triplet annihilation upconversion (TTA-UC) is a process that exploits as emitters organic molecules that would remove or mitigate these limitations. Nevertheless, no TTA-UC emitters have been reported to be able to absorb in the telecom region and very few in the region at wavelengths longer than 1000 nm. Here, we used Kohn-Sham density functional calculations to tune the triplet energy of tetracene, the parent molecule of a class of emitters for infrared light UC. We highlight three organic molecules, each with an existing synthetic procedure, as promising near-infrared (NIR) TTA-UC annihilators. Additionally, we computationally predict 5,12-bis-(<i>N</i>,<i>N</i>-diaminobenzene)-tetracene as an emitter for TTA-UC of light beyond 1250 nm. These findings pave the way for the design and development of organic molecules for upconverting the telecom-band NIR light.