Design of Lanthanide‐Based OLEDs with Remarkable Circularly Polarized Electroluminescence. (3rd November 2016)

• Record Type: Journal Article
• Authors: Zinna, Francesco; Pasini, Mariacecilia; Galeotti, Francesco; Botta, Chiara; Di Bari, Lorenzo; Giovanella, Umberto
• Is Part Of: Advanced functional materials. Volume 27:Number 1(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2016-11-03
• Subjects: chiral electroluminescence -- circular polarization -- interfacial layers -- lanthanides -- OLEDs; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201603719
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract : Organic light‐emitting diodes (OLEDs) able to directly emit circularly polarized (CP) electroluminescence (CP‐OLEDs) are rapidly gaining much interest, due to their possible applications in displays with antiglare filters and 3D displays. Development of more efficient CP‐OLEDs can open their use also in point‐of‐care and personalized diagnostic tools, since CP light alteration can be related to health state of irradiated tissues. In this work it is shown that the performance of chiral europium complex‐based CP‐OLEDs can be improved both in terms of external quantum efficiency (measured on all the Eu bands) and degree of polarization of emitted photons (as measured by the dissymmetry factor g EL ), by proper active layer formulation and through a fine tuning of the architecture of the device. Polarization performances ( g EL = −1) are obtained about three times higher than for any other CP‐OLED reported so far. Moreover, for the first time, it is shown that the position of the recombination zone (RZ) plays a major role on the polarization outcomes. In order to rationalize these results the level of light polarization is related to the position of the RZ allied with the reflection on the cathode through a simple mathematical model. The values predicted by this model are in qualitative agreement with the experimental ones. Abstract : Lanthanide‐based organic light‐emitting diodes (OLEDs) with remarkable circularly polarized electroluminescence are designed. 75% of the emitted photons at 595 nm are circularly polarized with enhanced external quantum efficiency with respect to our earlier proof‐of‐concept achievement. For the first time the main factors affecting circularly polarized OLEDs performance are identified by combining experimental data and modeling to bring the technology to the next readiness level.