Highly Conductive and Transparent Large‐Area Bilayer Graphene Realized by MoCl₅ Intercalation

Abstract

Bilayer graphene (BLG) comprises a 2D nanospace sandwiched by two parallel graphene sheets that can be used to intercalate molecules or ions for attaining novel functionalities. However, intercalation is mostly demonstrated with small, exfoliated graphene flakes. This study demonstrates intercalation of molybdenum chloride (MoCl ) into a large-area, uniform BLG sheet, which is grown by chemical vapor deposition (CVD). This study reveals that the degree of MoCl intercalation strongly depends on the stacking order of the graphene; twist-stacked graphene shows a much higher degree of intercalation than AB-stacked. Density functional theory calculations suggest that weak interlayer coupling in the twist-stacked graphene contributes to the effective intercalation. By selectively synthesizing twist-rich BLG films through control of the CVD conditions, low sheet resistance (83 Ω ▫ ) is realized after MoCl intercalation, while maintaining high optical transmittance (≈95%). The low sheet resistance state is relatively stable in air for more than three months. Furthermore, the intercalated BLG film is applied to organic solar cells, realizing a high power conversion efficiency.

Formation of environmentally stable hole-doped graphene films with instantaneous and high-density carrier doping via a boron-based oxidant

“…As the next step, we investigated the effect of carrier doping on film transparency because, in most transparent electrodes, the film conductivity and transparency typically follow opposite trends. 3,[18][19][20][22][23][24][25][26]28 Figure 2d shows transmission spectra of the pristine (gray) and doped (red) graphene samples on a glass substrate (Sample #1); these samples were used for I-V measurements ( Fig. 2c).…”

“…is a new class of hole-doping reagent that can fulfill four important requirements of graphene doping: a high carrier density, the air stability of doped graphene, a facile solution-based doping process, and negligible transmittance reduction after doping. Moreover, we successfully fabricated organic photovoltaic cells (OPVs) 28,29,36 using the Mes 2 B + [(C 6 F 5 ) 4 B] − -doped graphene as electrodes; the resultant devices exhibit an enhanced device performance in terms of the fill factor (FF) and power conversion efficiency (PCE). As shown in supplementary S7 ( Fig.…”

“…To date, numerous accounts of the chemical doping of graphene have been reported. 3,[18][19][20][21][22][23][24][25][26][27][28][29] However, none of them fulfills all four of the aforementioned requirements.…”

Intercalation Strategy in 2D Materials for Electronics and Optoelectronics

“…Figure a exhibits the intercalation process of MoCl 5 in bilayer graphene (BLG). [ 94 ] A small amount of MoO 3 facilitates the formation of intermediate and releasing Cl 2 , which is responsible for the stage‐1 intercalation of MoCl 5 . As shown in Figure 6b, for pristine BLG, the intensity ratio of 2D band to G ( I 2D /I G ) is related to the stacking order of layers.…”

Isothermal growth and stacking evolution in highly uniform AB-stacked bilayer graphene

“…42 This is because the yield of intercalation has been reported to be higher in T-BLG than in AB-BLG, highlighting the importance of having a synthesis method that can control the twist/AB ratio in large-area BLG. 42 Fig. 3c), which corresponds to the lattice constant of graphene.…”