title: Highly Simplified Reddish Orange Phosphorescent Organic Light-Emitting Diodes Incorporating a Novel Carrier- and Exciton-Confining Spiro-Exciplex-Forming Host for Reduced Efficiency Roll-off.
abstract: A novel exciplex-forming host is applied so as to design highly simplified reddish orange light-emitting diodes (OLEDs) with low driving voltage, high efficiency, and an extraordinarily low efficiency roll-off, by combining N,N-10-triphenyl-10H-spiro [acridine-9,9'-fluoren]-3'-amine (SAFDPA) with 4,7-diphenyl-1,10-phenanthroline (Bphen) doped with trivalent iridium complex bis(2-methyldibenzo[f,h]quinoxaline) (acetylacetonate)iridium(III) (Ir(MDQ)2(acac)). The reddish orange OLEDs achieve a strikingly high power efficiency (PE) of 31.80 lm/W with an ultralow threshold voltage of 2.24 V which is almost equal to the triplet energy level of the phosphorescent reddish orange emitting dopant. The power efficiency of the device with the exciplex-forming host is enhanced, achieving 36.2% mainly owing to the lower operating voltage by the novel exciplex forming cohost, compared with the reference device (23.54 lm/W). Moreover, the OLEDs show extraordinarily low current efficiency (CE) roll-off to 1.41% at the brightness from 500 to 5000 cd/m2with a maximal CE of 32.87 cd/A (EQEmax= 11.01%). The devices display a good reddish orange color (CIE of (0.628, 0.372) at 500 cd/m2) nearly without color shift with increasing brightness. Co-host architecture phosphorescent OLEDs show a simpler device structure, lower working voltage, and a better efficiency and stability than those of the reference devices without the cohost architecture, which helps to simplify the OLED structure, lower the cost, and popularize OLED technology.
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School, Peking University , Shenzhen 518055, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Xu
authors.affiliation: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu 215123, China.
authors.forename: Ye-Xin
authors.initials: YX
authors.lastname: Zhang
authors.affiliation: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu 215123, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Wang
authors.affiliation: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu 215123, China.
authors.forename: Chen-Chao
authors.initials: CC
authors.lastname: Huang
authors.affiliation: Key Laboratory of Flexible Electronics and Institute of Advanced Materials, Jiangsu National Synergistic Innovation Centre for Advanced Materials, Nanjing Tech University , Nanjing 211816, China.|Department of Physics, International Islamic University , Islamabad 44000, Pakistan.
authors.forename: Imran
authors.identifier: http://orcid.org/0000-0001-5322-8656
authors.initials: I
authors.lastname: Murtaza
authors.affiliation: School of Advanced Materials, Peking University Shenzhen Graduate School, Peking University , Shenzhen 518055, China.|Key Laboratory of Flexible Electronics and Institute of Advanced Materials, Jiangsu National Synergistic Innovation Centre for Advanced Materials, Nanjing Tech University , Nanjing 211816, China.
authors.forename: Hong
authors.identifier: http://orcid.org/0000-0001-5877-359X
authors.initials: H
authors.lastname: Meng
authors.affiliation: Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University , Suzhou, Jiangsu 215123, China.
authors.forename: Liang-Sheng
authors.identifier: http://orcid.org/0000-0002-2352-9666
authors.initials: LS
authors.lastname: Liao
keywords: OLED; efficiency roll-off; exciplex-forming host; hole-transport-material-free; reddish orange phosphorescence