Simple and rapid cleaning of graphenes with a ‘bubble-free’ electrochemical treatment

Abstract

A simple and rapid ‘bubble-free’ electrochemical cleaning process is developed to clean and de-dope unintentionally contaminated and doped graphenes.

Full-surface emission of graphene-based vertical-type organic light-emitting transistors with high on/off contrast ratios and enhanced efficiencies

“…The above characteristics highlight several interesting features of our Gr-VOLET. To investigate its distinct characteristics further, we tested three types of SLG materials as source electrodes; (i) p-doped SLG with FeCl 3 (hereafter SLG 1 for fabricating Gr-VOLET 1 ), where FeCl 3 doping is done spontaneously during the graphene transfer process, as shown previously 35 ; (ii) pristine (intrinsic) SLG, cleaned by an electrochemical process 35 , as a comparative reference (SLG 2 for Gr-VOLET 2 ); and (iii) SLG coated with a conventional hole-injection layer (HIL) of (3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) 34 as a second comparative reference (SLG 3 for Gr-VOLET 3 ). The basic properties of the three SLG sources (with low porosities below 0.1%) are shown in Supplementary Fig.…”

“…In this article, we report on the first use of a VOLET with a homogeneous, smooth, and easily processable graphene layer as the source electrode, together with an emissive channel layer. As a two-dimensional material in the form of a single layer with a carbon-based hexagonal lattice structure bonded in the sp 2 configuration 30–32 , graphene has been used as a transparent electrode material in small OLEDs, as a proof of concept 33–35 . Despite the low dimensionality of graphene, similar to that of CNTs 31,32 , the successful operation of full-surface EL light emission from a VOLET based on graphene has not yet been reported, as the work function (~4.6 eV) of pristine graphene is too low for the hole injection 33–35 .…”

Vertical-Type Organic Light-Emitting Transistors with High Effective Aperture Ratios

“…Synthesis and transfer of SLG: The procedure used for transferring the chemicalvapor-deposition (CVD)-grown graphene onto a target substrate [40][41][42][43][44][45], in this case an FET substrate, a VOLET substrate, or a glass substrate, is described below. The first step involves the CVD growth of graphene on a copper (Cu) foil [42][43][44][45].…”

“…The graphene on the back side of the Cu foil was removed by atmosphericpressure oxygen plasma. Next, a PMMA-coated Cu/Gr (Cu/Gr/PMMA) block (width: 4 mm, length: 20 mm) was floated on an aqueous FeCl 3 etching solution used to etch the Cu foil entirely, at 50°C for 20 min [40]. Next, the Gr/PMMA block was rinsed with deionized (DI) water two to five times (10 min) and transferred onto a target substrate, after which the graphene-transferred substrate was dried under reduced pressure (~1 Pa) for 1 h and left in air for 24 h. The PMMA layer was then removed by dissolving the PMMA layer in chloroform (~60 min), monochlorobenzene (~30 min), and chloroform again (~30 min), to obtain a SLG source electrode.…”

“…In this study, a transferred SLG was investigated as a source contact, where the FeCl 3 doping is processed spontaneously during the graphene transfer process [40]. The basic properties of the three SLG sources are shown in Figures 3 and 4 and are summarized in Table 1.…”