The Quantum Efficiency Roll-Off Effect in Near-Infrared Organic Electroluminescent Devices with Iridium Complexes Emitters

Materials

Waldemar Stampor¹  Daniel Pelczarski¹  Piotr Grygiel¹  Alberto Bossi²  Sagar Kesarkar²  Wojciech Mróz³ 

[1] Department of Physics of Electronic Phenomena, Faculty of Applied Physics and Mathematics, Gdańsk University of Technology, Narutowicza 11/12, 80–233 Gdańsk, Poland;Institute of Chemical Science and Technologies “G. Natta”, National Research Council (CNR-SCITEC), Via Fantoli 16/15, 20138 Milan and SmartMatLab Center, Via C. Golgi 19, 20133 Milan, Italy;Institute of Macromolecules’ Study (ISMAC), National Research Council (CNR), Via E. Bassini 15, 20133 Milan, Italy;

关键词: OLEDs;    infrared emitters;    iridium complex;    quantum efficiency roll-off;    triplet-triplet annihilation;   

DOI  :  10.3390/ma13081855

来源: DOAJ

【 摘 要 】

The electroluminescence quantum efficiency roll-off in iridium(III)-based complexes, namely Ir(iqbt)₂(dpm) and Ir(iqbt)₃ (iqbt = 1 (benzo[b]thiophen-2-yl)-isoquinolinate, dpm = 2,2,6,6-tetramethyl-3,5-heptanedionate) utilized as near-infrared emitters in organic light emitting diodes with remarkable external quantum efficiencies, up to circa 3%, 1.5% and 1%, are measured and analyzed. With a 5–6 weight% of emitters embedded in a host matrix, the double-layer solution-processed structure as well as analogous three-layer one extended by a hole-conducting film are investigated. The triplet-polaron, the Onsager electron-hole pair dissociation and the triplet-triplet annihilation approaches were used to reproduce the experimental data. The mutual annihilation of triplets in iridium emitters was identified as prevailingly controlling the moderate roll-off, with the interaction between those of iridium emitters and host matrixes found as being less probable. Following the fitting procedure, the relevant rate constant was estimated to be $\left(0.5-12\right)\times {10}^{-12}$ cm³/s, values considered to be rather too high for disordered organic systems, which was assigned to the simplicity of the applied model. A coexistence of some other mechanisms is therefore inferred, ones, however, with a less significant contribution to the overall emission quenching.

【 授权许可】

Unknown