title: Lithium hydride doped intermediate connector for high-efficiency and long-term stable tandem organic light-emitting diodes.
abstract: Lithium hydride (LiH) is employed as a novel n-dopant in the intermediate connector for tandem organic light-emitting diodes (OLEDs) because of its easy coevaporation with other electron transporting materials. The tandem OLEDs with two and three electroluminescent (EL) units connected by a combination of LiH doped 8-hydroxyquinoline aluminum (Alq3) and 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) demonstrate approximately 2-fold and 3-fold enhancement in current efficiency, respectively. In addition, no extra voltage drop across the intermediate connector is observed. Particularly, the lifetime (T75%) in the tandem OLED with two and three EL units is substantially improved by 3.8 times and 7.4 times, respectively. The doping effect of LiH into Alq3, the charge injection, and transport characteristics of LiH-doped Alq3 are further investigated by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS).
authors.affiliation: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University , Suzhou, Jiangsu 215123, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Ding
authors.forename: Xun
authors.initials: X
authors.lastname: Tang
authors.forename: Mei-Feng
authors.initials: MF
authors.lastname: Xu
authors.forename: Xiao-Bo
authors.initials: XB
authors.lastname: Shi
authors.forename: Zhao-Kui
authors.initials: ZK
authors.lastname: Wang
authors.forename: Liang-Sheng
authors.initials: LS
authors.lastname: Liao
keywords: LiH; intermediate connector; long lifetime; n-type dopant; tandem OLEDs