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.

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.

Figures