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Micro/Nanostructure-Stimulated Light Manipulation For High Performance Organic Light-emitting Diodes

Posted on:2016-12-06Degree:MasterType:Thesis
Country:ChinaCandidate:Q D OuFull Text:PDF
GTID:2308330464455021Subject:Chemistry
Abstract/Summary:PDF Full Text Request
Organic light-emitting diodes(OLEDs) have recently gained increasing importance in applications of full-color display panels, eco-friendly interior lighting, and wearable intelligent electronics. Especially, tandem and white OLED technologies are considered as next-generation lighting system due to high efficiency, long lifetime, etc. Nevertheless, due to optical confinement and internal reflection, the light out-coupling efficiency for conventional OLEDs with planar architecture is limited to ~20%, although internal quantum efficiency for the electron-photon conversion already approaches ~100% with the use of phosphorescence or thermally activated delayed fluorescence. The development of light extraction technologies is thus an increasingly popular strategy to enhance the overall device efficiency in OLEDs.In this thesis, various optical loss channels in an OLED are reviewed and light manipulation characteristics of photonic micro/nano-structures are addressed, especially for deterministic aperiodic nanostructures(DANs). On basis of perfect antireflective requirement with broadband omni-directional antireflectivity and polarization insensitivity, the novel DANs with three-dimentionally tapered subwavelength nanocone arrays are proposed for high-efficiency light extraction in OLEDs.An efficient tandem OLED employing DANs is realized with an enhancement factor of 4.99 and 10.49 for device efficiency and half-decay lifetime, respectively, as compared to the planar single-unit device. Here, the light out-coupling efficiency induced by DANs is over 2.6 times that of planar structure. Moreover, it is verified that the emission color with viewing angles is significantly stabilized with no obvious spectral distortion. Theoretical calculations clarify that the improved device performance could be primarily attributed to the effective extraction of the waveguide and surface plasmonic modes of the confined light over all the emission wavelengths and angles.Extremely power-efficient white OLEDs are further achieved, simutanenously addressing optical confinement and energy loss during electron-photon conversion. More specifically, an efficient white OLED structure is designated that combines DANs for broadband quasi-omnidirectional light manipulation and a multilayer energy cascade structure for energy-efficient photon generation. The power efficiency of the nanoatructured white OLED is recorded with 132.8 lm W-1(maximum) and 106.5 lm W-1(5000 cd m-2).It is anticipated that studies on light manipulation using DANs proposed in this thesis could open up new opportunities to promote high performance OLED panels for commercial applications.
Keywords/Search Tags:Organic light-emitting diodes, Light extraction, White OLED, Tandem OLED, Color stability, Operational stability
PDF Full Text Request
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