Colorless Polyimide

Subscriber access provided by University of Rochester | River Campus & Miner Libraries

Functional Nanostructured Materials (including low-D carbon)

Ultrathin Graphene Intercalation in PEDOT:PSS/Colorless PolyimideBased Transparent Electrodes for Enhancement of Optoelectronic Performance and Operational Stability of Organic Devices Do Hee Lee, Hyung Duk Yun, Eui Dae Jung, Jae Hwan Chu, Yun Seok Nam, Seunguk Song, Shi-Hyun Seok, Myoung Hoon Song, and Soon-Yong Kwon ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 16 May 2019 Downloaded from http://pubs.acs.org on May 16, 2019

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 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 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.

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 50 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

Ultrathin Graphene Intercalation in PEDOT:PSS/Colorless Polyimide-Based Transparent Electrodes for Enhancement of Optoelectronic Performance and Operational Stability of Organic Devices

Do Hee Lee, Hyung Duk Yun, Eui Dae Jung, Jae Hwan Chu, Yun Seok Nam, Seunguk Song, Shi-Hyun Seok, Myoung Hoon Song, and Soon-Yong Kwon*

School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea

* Corresponding authors. E-mail addresses: [email protected]

ABSTRACT: A novel flexible transparent electrode (TE) having a trilayer-stacked geometry, and high optoelectronic performance and operational stability was fabricated by the spin coating method. The trilayer was composed of an ultrathin graphene (Gr) film sandwiched between a

ACS Paragon Plus Environment

1

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 50

transparent and colorless polyimide (TCPI) layer and a methanesulfonic acid (MSA)-treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)

(PEDOT:PSS)

layer

containing

dimethylsulfoxide and Zonyl fluorosurfactant (designated as MSA-PDZ film). The introduction of solution-processable TCPI enabled the direct formation of high-quality graphene on organic surfaces with a clean interface. Stable doping of graphene with the MSA-PDZ film enabled tuning of the inherent work function and optoelectronic properties of the PEDOT:PSS films, leading to high figure of merit of ~70 in the as-fabricated TEs. Particularly, from multivariate and repetitive harsh environmental tests (T ≈ −50 to 90 oC, over 90 RH%), the TCPI/Gr heterostructure exhibited excellent tolerance to mechanical and thermal stresses and gas barrier properties that protected the MSA-PDZ film from exposure to moisture. Owing to the synergetic effect from the TCPI/Gr/MSA-PDZ anode structure, the TCPI/Gr/MSA-PDZ-based polymer light-emitting diodes (PLEDs) showed highly improved current and power efficiencies with maxima as high as 20.84 cd/A and 22.92 lm/W, respectively (comparable to those of indium-tinoxide-based PLEDs), in addition to much-enhanced mechanical flexibility.

KEYWORDS: flexible transparent electrodes, graphene, colorless polyimide, organic thin film, operational stability, flexible organic devices


2

Page 3 of 50 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


1. INTRODUCTION The development of flexible optoelectronics has led to the desire for transparent electrodes (TEs) with high optoelectronic and mechanical properties and long-term stability.1,2 Indium tin oxide (ITO) is the optoelectronic material most widely used in TEs owing to its high transparency, high conductivity, and electrochemical stability.3 However, ITO films have a number of drawbacks that limit their use in flexible optoelectronic devices, such as the mechanical brittleness, the dearth of indium in the earth, and the high-temperature and high-cost fabrication methods.1,4,5 Thus, the development of low-cost, large-area flexible TEs has become one of the most challenging areas in the field of flexible optoelectronics. Graphene (Gr) has attracted much attention as a rapidly emerging subclass of TE material especially for organic optoelectronic devices owing to its inherent advantages, such as its excellent optical transparency and mechanical and electrical properties.6,7 Currently, large-area graphene films are best synthesized via pyrolytic cracking of hydrocarbon gases at elevated temperatures (~1,000 oC) onto catalytic metal surfaces using chemical vapor deposition (CVD) process and later transferred to other substrates for the fabrication of target devices. Therefore, it is necessary to establish proper methods for transfer from the growth template to preserve the properties of the as-grown graphene8-12 and to develop additional doping processes to offset the inherently poor electrical conductance of the polycrystalline structure1,13-16. At this moment, direct formation of highquality graphene on organic surfaces and stable functionalization remain challenging issues in the practical application of graphene as a component in flexible optoelectronic devices. Extensive progress has been made through studies to overcome the CVD-grown graphene (CVD-Gr) transfer issues. Many support materials, including small organic molecules, polymers


3


Page 4 of 50

such as poly(methyl methacrylate) (PMMA), and thermal release tape, have been developed for graphene transfer.17-21 However, it is difficult to remove these supporting layers after the transfer process due to their strong interaction with graphene, resulting in organic residues, wrinkles and tears.18-21 This damage not only degrades the optoelectronic properties of graphene, but may also deteriorate the interface properties of graphene, leading to high surface roughness in thin-film devices such as polymer light-emitting diodes (PLEDs) and organic solar cells (OSCs).22-24 In order to circumvent the complicated process, direct transfer methods, such as roll-to-roll techniques8 and thin-film deposition processes,25,26 have been introduced for large-scale graphene transfer. However, the roll-to-roll process can impart undesirable stress to graphene, leading to cracks and voids.27 Moreover, the plastic substrates fabricated by the thin-film deposition process generally have a low glass-transition temperature (Tg) of under 200 °C and are inconvenient for use in high-temperature PLED and OSC processing.25,26 On account of these limitations, the implementation of high-quality graphene in PLEDs and OSCs is still challenging. Regarding the high-temperature processing issues, polyimide (PI) has attracted great attention as a commercially viable plastic substrate for flexible devices owing to its excellent thermal stability, chemical and mechanical resistances, and insulating properties.28-32 However, because of its insolubility and infusibility, conventional solution processing is difficult, and the opaqueness of PI (transmittances of 90% and T ≈ 50

oC).

(e) Repetitive analysis of

TCPI/Gr/MSA-PDZ on PDMS-coated glass under multivariate harsh environmental conditions for 60 h (5 cycles).


47


Figure 4.

Page 48 of 50

Device structure and performances of TCPI/Gr/MSA-PDZ anode-based

flexible PLEDs. (a) Schematic illustrations and energy level diagram of flexible PLED with TCPI/Gr/MSA-PDZ anode. (b) Current density as a function of voltage, (c) luminance as a function of current density, (d) power efﬁciency as a function of voltage


48

Page 49 of 50 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


for the PLED devices with TCPI/Gr/MSA-PDZ, PET/Gr(CT)/MSA-PDZ, and ITO anodes. (e) Photograph of the flexible PLED with TCPI/Gr/MSA-PDZ anode. (f) Normalized luminance of flexible PLED at 5 V as a function of bending cycles, with a bending radius of ~5 mm.

Table 1. Comparison of the performances of SY-based PLEDs with different anode structures

Rs of Anode [Ω·sq–1]

Luminance, max [cd m-2]

CE, max [cd A--1]

PE, max [lm W-1]

EQE, max [%]

Glass/ITO

8

69027 (99,791)

14.05 (16.90)

11.35 (13.84)

4.74 (5.49)

PET/ITO

40

22570 (34941)

11.92 (14.14)

8.14 (9.90)

3.75 (4.30)

TCPI/Gr/MSA-PDZ

48.6

15074 (38351)

15.82 (20.84)

12.86 (22.92)

5.64 (7.25)

PET/Gr(CT)/MSA-PDZ

46.1

5772.7 (8559.1)

8.30 (11.00)

7.10 (9.25)

3.00 (3.97)

Electrode Structure


49


Page 50 of 50

A Table of Contents (TOC) graphic:


50

Colorless Polyimide

Recommend Documents