Surface Control of Planarization Layer on Embossed Glass for Light Extraction in OLEDs

Doo-Hee Cho, Jin-Wook Shin, Jaehyun Moon, Seung Koo Park, Chul Woong Joo, Nam Sung Cho, Jin Woo Huh, Jun-Han Han, Jonghee Lee, Hye Yong Chu, Jeong-Ik Lee
2014 ETRI Journal  
We developed a highly refractive index planarization layer showing a very smooth surface for organic lightemitting diode (OLED) light extraction, and we successfully prepared a highly efficient white OLED device with an embossed nano-structure and highly refractive index planarization layers. White OLEDs act as an internal out-coupling layer. We used a spin-coating method and two types of TiO 2 solutions for a planarization of the embossed nano-structure on a glass substrate. The first TiO 2
more » ... The first TiO 2 solution was TiO 2 sol, which consists of TiO 2 colloidal particles in an acidic aqueous solution and several organic additives. The second solution was an organic and inorganic hybrid solution of TiO 2 . The surface roughness (R a ) and refractive index of the TiO 2 planarization films on a flat glass were 0.4 nm and 2.0 at 550 nm, respectively. The J-V characteristics of the OLED including the embossed nano-structure and the TiO 2 planarization film were almost the same as those of an OLED with a flat glass, and the luminous efficacy of the aforementioned OLED was enhanced by 34% compared to that of an OLED with a flat glass.
doi:10.4218/etrij.14.0113.0845 fatcat:qiuuvezb4zgy3g2xuhnxezn5ry