# Thiadiazolobenzotriazole-Based Donor–Acceptor Terpolymers That Can Be Processed from Green Solvents and Deliver 950 nm Emission in Light-Emitting Electrochemical Cells

## TL;DR

Scientists created new polymer materials that emit light at 950 nm using eco-friendly solvents, which could be useful for various applications.

## Contribution

The novel contribution is the design of terpolymers with 950 nm emission processed from green solvents.

## Key findings

- The terpolymers emit light at 935 nm and 950 nm in devices.
- They are processed from a water:ethanol solvent blend.
- The devices show fast turn-on and low voltage operation.

## Abstract

Organic semiconductors that deliver emission with a wavelength
exceeding 900 nm can enable a wide range of applications, but the
unfortunate fact is that only a small number of such emitters have
been synthesized and have demonstrated emissive function in devices.
Here, this issue is addressed through the design and synthesis of
two terpolymers that comprise a low energy-gap thiophene-thiadiazolobenzotriazole
(TBTzTD) donor–acceptor unit as the minority guest incorporated
in a majority donor–acceptor conjugated copolymer host, being
either thiophene-quinoxaline (TQ) or thiophene-difluoroquinoxaline
(TQ2F). These terpolymers are further endowed with high solubility
in benign hydrophilic solvents through the grafting of branched oligo­(ethylene
glycol) side chains onto the quinoxaline unit. The application function
of the terpolymer emitters is demonstrated through their implementation
in light-emitting electrochemical cells (LECs). It is notable from
a sustainability perspective that the emitter is metal free and that
the single-layer LEC active material is cast from an environmentally
benign water:ethanol solvent blend. From an application perspective,
it is attractive that the terpolymer-LEC devices feature a very fast
turn-on to significant radiance at low voltage and that they deliver
emission with a peak wavelength of 935 nm with TQ-TBTzTD as the emitter
and 950 nm with TQ2F-TBTzTD as the emitter.