Flexion bonding transfer of multilayered graphene as a top electrode in transparent organic light-emitting diodes

Jong Tae Lim,Hyunsu Cho,Byoung-Gon Yu,Jun-Han Han,Bong Kuk Lee,Seong Chu Lim,Hyunkoo Lee,Nam Sung Cho,Jonghyurk Park,Jeong-Ik Lee,Jong-Heon Yang,Byoung-Hwa Kwon,Chi-Sun Hwang,Jaesu Kim

doi:10.1038/srep17748

Abstract

Graphene has attracted considerable attention as a next-generation transparent conducting electrode, because of its high electrical conductivity and optical transparency. Various optoelectronic devices comprising graphene as a bottom electrode, such as organic light-emitting diodes (OLEDs), organic photovoltaics, quantum-dot LEDs, and light-emitting electrochemical cells, have recently been reported. However, performance of optoelectronic devices using graphene as top electrodes is limited, because the lamination process through which graphene is positioned as the top layer of these conventional OLEDs is a lack of control in the surface roughness, the gapless contact, and the flexion bonding between graphene and organic layer of the device. Here, a multilayered graphene (MLG) as a top electrode is successfully implanted, via dry bonding, onto the top organic layer of transparent OLED (TOLED) with flexion patterns. The performance of the TOLED with MLG electrode is comparable to that of a conventional TOLED with a semi-transparent thin-Ag top electrode, because the MLG electrode makes a contact with the TOLED with no residue. In addition, we successfully fabricate a large-size transparent segment panel using the developed MLG electrode. Therefore, we believe that the flexion bonding technology presented in this work is applicable to various optoelectronic devices.

Highlights

They should not damage the organic layers during the deposition process
We demonstrate a dry laminating technology for the fabrication of a top graphene-electrode-based Transparent OLEDs (TOLEDs) (G-TOLED), which enables uninterrupted contact by impurities and bending stress between the multilayered graphene (MLG) and the top organic layer with the flexion bank patterns
The measured efficiencies were slightly lower than the simulated values, because the actual devices did not have an internal efficiency of unity as a result of electrical loss. These results suggest that the reduced surface plasmon polariton (SPP) mode in the G-TOLED does not fully convert to the air mode, but the other modes in the G-TOLED are re-distributed

Summary

Introduction

They should not damage the organic layers during the deposition process. it is necessary to obtain the appropriate energy level alignment between the organic layer and TCTE in order to facilitate efficient charge injection[8]. The use of STMs as top electrodes in OLEDs causes considerable light loss during the light out-coupling process This is because STMs have strong absorption and a strong surface plasmon polariton (SPP) mode at the interface between the top organic layer and the TCTE22. Reported graphene top electrodes in light-emitting devices have been prepared using wet transfer method or high-temperature thermal treatment[8,20]. These graphene transfer processes limit the materials and structures of these devices, leading to poor device performance. We demonstrate a dry laminating technology for the fabrication of a top graphene-electrode-based TOLED (G-TOLED), which enables uninterrupted contact by impurities and bending stress between the MLG and the top organic layer with the flexion bank patterns. In terms of optical and electrical device characteristics, the G-TOLED exhibits superior performance to a thin-Ag top-electrode-based TOLED (Ag-TOLED)

Methods

Results

Conclusion