title: Highly Efficient and Low Turn-On Voltage Quantum Dot Light-Emitting Diodes by Using a Stepwise Hole-Transport Layer.
abstract: Highly efficient red quantum dot light-emitting diodes (QD-LEDs) with a very high current efficiency of 16 cd/A were demonstrated by adopting stepwise hole-transport layers (HTLs) consisting of 4,4'-N,N'-dicarbazole-biphenyl (CBP) combined with N,N'-dicarbazolyl-3,5-benzene (mCP). The mCP layer plays two important roles in this kind of QD-LEDs. One is that it can block the electron to leak into the HTL due to its higher LUMO (LUMO = the lowest unoccupied molecular orbital) energy level than that of CBP; and the other is it can separate the carrier accumulation zone from the exciton formation interface, which is attributed to the stepwise hole-transport layer structure. Moreover, the lower HOMO (HOMO = the highest occupied molecular orbital) energy level of mCP decreases the hole-injection barrier from the HTL to the QD emitting layer, which improves the charge carrier balance injected into the QD layer, reducing the turn-on voltage of QD-LEDs fabricated with the stepwise HTL structure.
authors.affiliation: †State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.
authors.forename: Wenyu
authors.initials: W
authors.lastname: Ji
authors.affiliation: †State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Lv
authors.affiliation: †State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.
authors.forename: Pengtao
authors.initials: P
authors.lastname: Jing
authors.affiliation: ‡Department of Physics, Jilin University, Changchun 130012, China.
authors.forename: Han
authors.initials: H
authors.lastname: Zhang
authors.affiliation: †State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China.|‡Department of Physics, Jilin University, Changchun 130012, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
authors.affiliation: ‡Department of Physics, Jilin University, Changchun 130012, China.
authors.forename: Hanzhuang
authors.initials: H
authors.lastname: Zhang
authors.affiliation: §Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education, Jilin Normal University, Siping 136000, China.
authors.forename: Jialong
authors.initials: J
authors.lastname: Zhao
keywords: charge accumulation; leakage current; light emitting diodes; quantum dots; stepwise hole-injection layer