Molecular glasses based on 1,8-naphthalimide and triphenylamine moieties as bipolar red fluorescent OLED emitters with conventional versus TADF hosting

Naveen Masimukku; Malek Mahmoudi; Dmytro Volyniuk; Asta Dabuliene; Simas Macionis; Vitaly Matulis; Dmitry Lyakhov; Juozas V Grazulevicius

doi:10.1016/j.saa.2022.122185

Molecular glasses based on 1,8-naphthalimide and triphenylamine moieties as bipolar red fluorescent OLED emitters with conventional versus TADF hosting

Spectrochim Acta A Mol Biomol Spectrosc. 2023 Mar 5:288:122185. doi: 10.1016/j.saa.2022.122185. Epub 2022 Nov 30.

Authors

Naveen Masimukku¹, Malek Mahmoudi¹, Dmytro Volyniuk¹, Asta Dabuliene¹, Simas Macionis¹, Vitaly Matulis², Dmitry Lyakhov³, Juozas V Grazulevicius⁴

Affiliations

¹ Department of Polymer Chemistry and Technology, Kaunas University of Technology, K. Baršausko g. 59, Kaunas 51423, Lithuania.
² Belarusian State University, 220030 Minsk, Belarus.
³ Computer, Electrical and Mathematical Science and Engineering Division, 4700 King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
⁴ Department of Polymer Chemistry and Technology, Kaunas University of Technology, K. Baršausko g. 59, Kaunas 51423, Lithuania. Electronic address: juozas.grazulevicius@ktu.lt.

PMID: 36481536
DOI: 10.1016/j.saa.2022.122185

Abstract

Three new donor-acceptor molecular glasses were designed and synthesized linking 1,8-naphthalimide and triphenylamino groups though the different bridges. The comprehensive characterization of the compounds was carried out using theoretical and experimental approaches. The compounds showed efficient orange-red emission in solid state with photoluminescence intensity maxima in the range of 584-654 nm. The compounds showed extremely high thermal stability with 5 % weight loss temperatures up to 477 °C. They formed molecular glasses with glass-transition temperatures in the range of 161-186 °C. The fabricated organic light-emitting diodes (OLEDs) based on the developed emitters and conventional host showed maximum external quantum efficiency of 2.5 % in the best case. This value was increased up to 4.7 % by the usage of the host exhibiting thermally activated delayed fluorescence (TADF). OLED containing the TADF host displayed orange emission peaking at 589 nm with colour coordinates x of 0.53 and y of 0.45 combined with power efficiency of 6.7 lm·W^-1 and current efficiency of 11.8 cd·A^-1. Time-resolved electroluminescence technique was used to study the effect of the different guest-host systems on exciton utilization efficiency in devices based on the same emitter exhibiting prompt fluorescence and on the conventional or TADF hosts.

Keywords: 1,8-naphthalimide; Emitter; OLED; Time-resolved electroluminescence; Triphenylamine.