Highly Simplified Tandem Organic Light-Emitting Devices

Mar 8, 2017 - School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen 518055, China. § Key Laboratory of Flexible Electro...
0 downloads 9 Views 2MB Size
Subscriber access provided by University of Newcastle, Australia

Article

Highly Simplified Tandem Organic Light-emitting Devices Incorporating a Green Phosphorescence Ultrathin Emitter within a Novel Interface Exciplex for High Efficiency Ting Xu, Jun-Gui Zhou, Chen-Chao Huang, Lei Zhang, Man Keung Fung, Imran Murtaza, Hong Meng, and Liang-Sheng Liao ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b16094 • Publication Date (Web): 08 Mar 2017 Downloaded from http://pubs.acs.org on March 9, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Highly Simplified Tandem Organic Light-Emitting Devices Incorporating a Green Phosphorescence Ultrathin Emitter within a Novel Interface Exciplex for High Efficiency Ting Xua,b, Jun-Gui Zhoua, Chen-Chao Huanga, Lei Zhanga, Man-Keung Funga, Imran Murtazac,d, Hong Mengb,c* and Liang-Sheng Liaoa* a

Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute

of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China b

School of Advanced Materials, Shenzhen Graduate School, Peking University,

Shenzhen 518055, China c

Key Laboratory of Flexible Electronics and Institute of Advanced Materials, Jiangsu

National Synergistic Innovation Centre for Advanced Materials, Nanjing Tech University, Nanjing 211816, China d

Department of Physics, International Islamic University, Islamabad 44000, Pakistan

KEYWORDS Organic light-emitting diodes, Tandem structure, Interface exciplex, Ultrathin emissive layers, Current efficiency

1

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 28

ABSTRACT

Herein, we report a novel design philosophy of tandem OLEDs incorporating a doping-free green phosphorescent Bis[2-(2-pyridinyl-N)phenyl-C](acetylacetonato) iridium(III) (Ir(ppy)2(acac) ) as ultrathin emissive layer (UEML) into a novel interface-exciplex-forming cyclohexane

(TAPC)

and

structure

of

1,1-Bis[(di-4-tolylamino)

1,3,5-tri(p-pyrid-3-yl-phenyl)benzene

phenyl]

(TmPyPB).

Particularly, relatively low working voltage and remarkable efficiency are achieved and the designed tandem OLEDs obtain a peak current efficiency of 135.74 cd/A (EQE=36.85 %) which is two times higher than 66.2 cd/A (EQE=17.97 %) of the device with a single emitter unit. This might be one of the highest efficiencies of OLEDs applying ultrathin emitters without light extraction. Moreover, with the proposed structure, the color gamut of the displays can be effectively increased from 76 % to 82 % NTSC if the same red and blue emissions as those in the NTSC are applied. A novel form of harmonious fusion among interface exciplex, UEML, and tandem structure is successfully realized, which shed light on further development of ideal OLEDs structure with high efficiency, simplified fabrication, low power consumption, low cost and improved color gamut, simultaneously.

2

ACS Paragon Plus Environment

Page 3 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

1. Introduction After the invention of first succinct organic light-emitting device (OLED) with twolayer structure in 1987 by C.W Tang,1 flat-panel displays and illumination applications based on OLED technology have developed sharply due to their attractive features such as simple fabrication process, devisable smart structure, impressive color rendering, ultra-thin structure, wide viewing angles, abundant organic materials, light-weight and high compatibility with flexible substrates.2-9 OLEDs stacking by two or more emitter units have drawn enormous attention due to their impressive current efficiency (CE), brightness, external quantum efficiency (EQE), luminous efficiency, and device life time

compared

to

conventional

OLEDs.10-14

However,

stacking

multiple

electroluminescence (EL) units in tandem OLEDs increases driving voltage and complicates fabrication process relative to their standard single unit counterparts. Moreover, commercial OLED products are still so pricey for consumers.15 Therefore it is urgently needed to boil down the OLEDs structure and fabrication technology to reduce the cost of products.15 To be specific, in typical tandem OLEDs, the doping technique needs the careful selection of appropriate hosts for different dopants in hostguest emitter system.16 Besides, the controlment of codeposition rate and dopant concentration in the fabrication procedure is complex and not absolutely accurate, which tends to lower the yield in production line. Moreover, the physical vapor deposition equipment needs to be remoulded with adequate sensors and evaporator sources in order to realize complex device fabrication of tandem OLEDs, which increase their manufacturing costs. 3

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

To loosen the bottlenecks, the doping-free technology applying ultrathin emitting nanolayers (