High light extraction performance using evanescent waves for top emission OLED applications with thin film encapsulation

Hye In Yang, Nagarjuna Naik Mude, Jin Young Kim, Jun Hyeog Oh, Ramchandra Pode, and Jang Hyuk Kwon,

Opt. Express 31, 18407-18419 (2023)

https://doi.org/10.1364/OE.487301

The study presents an enhanced top emission OLED (TEOLED) device structure that significantly improves light extraction, specifically by addressing waveguide mode loss in the thin film encapsulation (TFE) layer. By introducing a low refractive index (RI) layer between the capping layer (CPL) and the aluminum oxide (Al2O3) layer, the device manipulates evanescent waves to redirect trapped light within the device, increasing its extraction. This novel TFE structure (CPL/low RI layer/Al2O3/polymer/Al2O3) led to a 23% increase in current efficiency and a 26% enhancement in the blue index value for the blue TEOLED device. This method shows significant potential for advancing flexible optoelectronic device encapsulation technologies.

How Setfos was used

SETFOS 5.1 is used as an optical simulator. The RI of the glass substrate, indium tin oxide (ITO), and organic layers are taken as ∼1.5, 1.8∼2.0, and ∼1.8, respectively. The RI and extinction coefficient of silver (Ag) and magnesium (Mg):Ag (10:1) used as an anode and cathode, respectively, are taken from the reported values. For the EML, the thin film photoluminescence spectrum of 2,12-di-tert-butyl-N,N,5,9-tetrakis(4-(tert-butyl)phenyl)-5,9-dihydro-5,9-diaza-13bboranaphtho[ 3,2,1-de]anthracen-7-amine (DABNA-NP-TB) for the blue TEOLED device, bis[2- (2-pyridinyl-N)phenyl-C](acetylacetonato)iridium(III) for the green TEOLED device, and (bis(4- methyl-2-(3,5-dimethylphenyl)quinoline))Ir(III (tetramethylheptadionate) for the red TEOLED device are used.