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

## TL;DR

Researchers used computational methods to design organic molecules that can convert low-energy infrared light into higher-energy light, which is important for telecommunications.

## Contribution

The study introduces new organic molecules for efficient light upconversion in the silica telecom band, surpassing the 1250 nm limit.

## Key findings

- Three organic molecules with existing synthetic procedures are identified as promising near-infrared TTA-UC annihilators.
- 5,12-bis(N,N-diaminobenzene)tetracene is predicted as an emitter for TTA-UC beyond 1250 nm.
- Computational tuning of tetracene's triplet energy enables efficient light upconversion in the telecom band.

## Abstract

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(N,N-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.