title: Achieving Extreme Utilization of Excitons by an Efficient Sandwich-Type Emissive Layer Architecture for Reduced Efficiency Roll-Off and Improved Operational Stability in Organic Light-Emitting Diodes.
abstract: It has been demonstrated that the efficiency roll-off is generally caused by the accumulation of excitons or charge carriers, which is intimately related to the emissive layer (EML) architecture in organic light-emitting diodes (OLEDs). In this article, an efficient sandwich-type EML structure with a mixed-host EML sandwiched between two single-host EMLs was designed to eliminate this accumulation, thus simultaneously achieving high efficiency, low efficiency roll-off and good operational stability in the resulting OLEDs. The devices show excellent electroluminescence performances, realizing a maximum external quantum efficiency (EQE) of 24.6% with a maximum power efficiency of 105.6 lm W(-1) and a maximum current efficiency of 93.5 cd A(-1). At the high brightness of 5,000 cd m(-2), they still remain as high as 23.3%, 71.1 lm W(-1), and 88.3 cd A(-1), respectively. And, the device lifetime is up to 2000 h at initial luminance of 1000 cd m(-2), which is significantly higher than that of compared devices with conventional EML structures. The improvement mechanism is systematically studied by the dependence of the exciton distribution in EML and the exciton quenching processes. It can be seen that the utilization of the efficient sandwich-type EML broadens the recombination zone width, thus greatly reducing the exciton quenching and increasing the probability of the exciton recombination. It is believed that the design concept provides a new avenue for us to achieve high-performance OLEDs.
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Zhongbin
authors.initials: Z
authors.lastname: Wu
authors.affiliation: The Organic Photonics and Electronics Group, Department of Physics, Umeå University , SE-901 87 Umeå, Sweden.
authors.forename: Ning
authors.initials: N
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Liping
authors.initials: L
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Hengda
authors.initials: H
authors.lastname: Sun
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Jiaxiu
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Dezhi
authors.initials: D
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Qiao
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences , Changchun 130022, People's Republic of China.
authors.forename: Jiangshan
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Chemistry, King Saud University , Riyadh, Kingdom of Saudi Arabia.
authors.forename: Saad M
authors.initials: SM
authors.lastname: Alshehri
authors.affiliation: Department of Chemistry, King Saud University , Riyadh, Kingdom of Saudi Arabia.
authors.forename: Tansir
authors.initials: T
authors.lastname: Ahamad
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, University of Chinese Academy of Sciences , Changchun 130022, People's Republic of China.|Department of Chemistry, King Saud University , Riyadh, Kingdom of Saudi Arabia.
authors.forename: Dongge
authors.initials: D
authors.lastname: Ma
keywords: efficiency roll-off; extreme utilization; operational stability; organic light-emitting diodes; sandwich-type