Triazolobenzothiadiazole-Based Copolymers for Polymer Light-Emitting Diodes: Pure Near-Infrared Emission via Optimized Energy and Charge Transfer
Journal article, 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.A series of new near-infrared (NIR) emitting copolymers, based on a low band gap 6-(2-butyloctyl)-4,8-di(thiophen-2-yl)-[1,2,3]triazolo[4',5':4,5]benzo[1,2-c]-[1,2,5]thiadiazole (TBTTT) fluorophore copolymerized into a high band gap poly[3,3'-ditetradecyl-2,2'-bithiophene-5,5'-diyl-alt-5-(2-ethylhexyl)-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione-1,3-diyl] (P2TTPD) host backbone, for polymer light-emitting diode (PLED) applications is reported. PLEDs fabricated from the host polymer (P2TTPD-0) show external quantum efficiencies (EQEs) up to 0.49% at 690 nm, with turn-on voltage (Von) at only 2.4 V. By incorporating the TBTTT segments into the host polymer backbone, pure NIR emission peaking at ca. 900 nm is obtained with Von remaining below 5 V. This work demonstrates that such a low Von can be attributed to efficient intrachain energy and/or charge transfer to the TBTTT sites. When the NIR emitting copolymer (P2TTPD-10) is blended with P2TTPD-0, the TBTTT are confined to well-separated polymer chains. As a result, the EQE from the blend is lower and the Von higher than that obtained from the pure copolymer (P2TTPD-1.0) with equal content of TBTTT. An analogous copolymer (P4T-1.0), consisting of poly[3,3'-ditetradecyl-2,2':5',2'':5'',2'''-quaterthiophene-5,5'''-diyl] (P4T) as the host and 1% TBTTT as the NIR emitter, further demonstrates that pure NIR emission can be obtained only through optimized molecular orbital energy levels, as in P2TTPD-1.0, which minimizes chances for either charge trapping or exciton splitting.

OLEDs

Fluorescent materials

Emission

Near-infrared

Conjugated polymers

Author

Petri Henrik Murto

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

A. Minotto

University College London (UCL)

A. Zampetti

University College London (UCL)

Xiaofeng Xu

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

Mats Andersson

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

F. Cacialli

University College London (UCL)

Ergang Wang

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Polymer Technology

Advanced Optical Materials

2195-1071 (eISSN)

12 2068-2076

Subject Categories

Materials Engineering

Chemical Sciences

Roots

Basic sciences

DOI

10.1002/adom.201600483

More information

Latest update

2/28/2018