Thermally Evaporated Organic/Ag/Organic Multilayer Transparent Conducting Electrode for Flexible Organic Light‐Emitting Diodes

• Published in: Advanced electronic materials Vol. 5; no. 10
• Main Authors: Bae, Hyeong Woo, Kim, Seong Keun, Lee, Subin, Song, Min‐Geun, Lampande, Raju, Kwon, Jang Hyuk
• Format: Journal Article
• Language: English
• Published: 01.10.2019
• Subjects: flexible OLED; thermally stable; transparent conducting electrodes; wetting inducer
• ISSN: 2199-160X; 2199-160X
• DOI: 10.1002/aelm.201900620

This paper reports an efficient, thermally stable, and high‐performance flexible multilayer transparent conducting electrode (TCE) by sandwiching an ultrathin Ag layer between a thermally evaporated small‐molecule organic wetting inducer, 1,4‐bis(2‐phenyl‐1,10‐phenanthrolin‐4‐yl)benzene and an organic antireflective capping layer, 1,4,5,8,9,11‐hexaazatriphenylene hexacarbonitrile for flexible organic light‐emitting diodes (OLEDs). This TCE demonstrates a high transmittance of about 81.34% at 550 nm and very low sheet resistance of 9.51 Ω sq−1 with excellent thermal stability under high‐temperature (100 °C for 72 h) conditions. These properties arise from the synergistic effect of coordinate bonding between the nitrogen of the phenanthroline moiety and the Ag atom which leads to a smooth and uniform Ag surface and the outstanding optical properties of the capping layer. Moreover, this TCE on a plastic substrate shows excellent mechanical flexibility and durability under continuous bending stress (bending radius of 5 mm) with a very slight increase in corresponding resistance (9.90 Ω sq−1) after 2000 bending cycles. The green phosphorescent OLED with this TCE reveals excellent current efficiency of 75.1 cd A−1 and external quantum efficiency of 23.1% at a luminance of 3000 cd m−2. These results suggest that the studied TCE will be very useful for next‐generation flexible active matrix OLED display applications. A thermally stable and high‐performance multilayer transparent conducting electrode, organic/Ag/organic (OAO) is investigated for organic light emitting diodes (OLEDs). This electrode shows excellent electro‐optical properties and mechanical flexibility as well as rigidity under continuous bending stress. The OLED device with an OAO electrode exhibits superior external quantum efficiency compared with the reference device.