Tae‐Woo Lee1,2, Taeyong Noh2, Hee-Won Shin3, Ohyun Kwon2, Jongjin Park2, Byoung Ki Choi2, Myeong Suk Kim2, Dong Woo Shin2, Yong Rok Kim3
1Department of Materials Science and Engineering Pohang University of Science and Technology San 31 Hyoja-dong, Nam-gu, Pohang Gyeongbuk 790-784 (Korea)
2Display Device and Processing Laboratory Samsung Advanced Institute of Technology Mt. 14‐1, Nongseo‐dong, Giheung‐gu, Yongin‐si Gyeonggi‐do 446‐712 (Korea)
3Photon Applied Functional Molecule Research Laboratory Department of Chemistry Yonsei University Seoul 120-749 (Korea)
Tóm tắt
AbstractAlthough significant progress has been made in the development of vacuum‐deposited small‐molecule organic light‐emitting diodes (OLEDs), one of the most desired research goals is still to produce flexible displays by low‐cost solution processing. The development of solution‐processed OLEDs based on small molecules could potentially be a good approach but no intensive studies on this topic have been conducted so far. To fabricate high‐performance devices based on solution‐processed small molecules, the underlying nature of the produced films and devices must be elucidated. Here, the distinctive characteristics of solution‐processed small‐molecule films and devices compared to their vacuum‐deposited counterparts are reported. Solution‐processed blue OLEDs show a very high luminous efficiency (of about 8.9 cd A–1) despite their simplified structure. A better hole‐blocking and electron‐transporting layer is essential for achieving high‐efficiency solution‐processed devices because the solution‐processed emitting layer gives the devices a better hole‐transporting capability and more electron traps than the vacuum‐deposited layer. It is found that the lower density of the solution‐processed films (compared to the vacuum‐deposited films) can be a major cause for the short lifetimes observed for the corresponding devices.
