Место издания:Enikolopov Institute of Synthetic Polymeric Materials of Russian Academy of Sciences Moscow
Первая страница:68
Последняя страница:68
Номер статьи:P12
Аннотация:Near-Infrared (NIR) Organic Light-Emitting Diodes (OLEDs) are promising as radiationsources for wearable devices (e.g., pulse oximeters, health monitoring sensors), lab-on-a-chipmicrofluidic sensing systems, and related applications. One of the key parameters determiningthe accuracy of analyte concentration detection is the emission bandwidth of the light sourceabsorbed by the analyte. Because it is directly related to the measurable concentration rangeand, consequently, to sensitivity. Lanthanide coordination compounds (CCs) combine narrowluminescence bands (10–15 nm FWHM) characteristic of lanthanide cations with broadopportunities for tuning the physicochemical properties of the organic ligand. Among all NIRemitting lanthanide cations, ytterbium (Yb3+) exhibits the highest efficiency, withphotoluminescence quantum yields (PLQY) reaching several percent. This makes NIROLEDs based on Yb3+ CCs particularly attractive for further investigation.In this study, a series of lanthanide CCs featuring substituted Schiff bases as emissive layers(EML) in OLEDs was investigated. Specifically, halogen-substituted Schiff bases werestudied for their enhanced solubility even in the form of Yb(L)(HL) complexes, enabling theformation of high-quality thin films for EML. Naphthyl- and pyrenyl-substituted ligandsdemonstrated improved electron transport due to the extended π-conjugated systems withinthe ligand structure. Electron-donating (di(phenyl)aminophenyl-) and electron-accepting(phenyl(oxadiazolyl)- and methyl(oxadiazolyl)-) hydrazone substituents were introduced toimprove charge carrier transport within the EML bulk. It was shown that the introduction ofeven a single halogen substituent (F or Br) significantly increases solubility in EtOH or THF,enabling high-quality EML film formation and enhancing the external current efficiency(ECE) of the OLED by a factor of two—from 50 to 100 µW/W. The combination of anelectron-donating and an electron-accepting ligand in a heteroleptic CC led to a 25%improvement in OLED efficiency compared to a mixture of two homoleptic CCs, from 110 to140 µW/W. Furthermore, optimization of the OLED heterostructure, particularly the chargetransport layers, for a Yb3+ CC bearing a naphthyl-substituted Schiff base enabled an ECE ofup to 441 µW/W, which, at the time of publication, was among the highest reported.
