Approaching the limits of transparency and conductivity in graphitic materials through lithium intercalation

Abstract

Various band structure engineering methods have been studied to improve the performance of graphitic transparent conductors; however, none has demonstrated an increase of optical transmittance in the visible range. Here we measure in situ optical transmittance spectra and electrical transport properties of ultrathin graphite (3-60 graphene layers) simultaneously during electrochemical lithiation/delithiation. On intercalation, we observe an increase of both optical transmittance (up to twofold) and electrical conductivity (up to two orders of magnitude), strikingly different from other materials. Transmission as high as 91.7% with a sheet resistance of 3.0 O per square is achieved for 19-layer LiC 6 , which corresponds to a figure of merit s dc /s opt ¼ 1,400, significantly higher than any other continuous transparent electrodes. The unconventional modification of ultrathin graphite optoelectronic properties is explained by the suppression of interband optical transitions and a small intraband Drude conductivity near the interband edge. Our techniques enable investigation of other aspects of intercalation in nanostructures.

Facile Doping and Work‐Function Modification of Few‐Layer Graphene Using Molecular Oxidants and Reductants

“…The intercalated dopant molecules are thus encapsulated resulting in stable bulk doping, as has been shown with various intercalants such as Br2, [32] FeCl3 [33] and Li. [34] Despite these advantages and opportunities, the vast majority of doping efforts reported to date have focused on SLG.…”

Transparent, conductive solution processed spincast 2D Ti2CTx (MXene) films

“…Ag-nanowires [27] are a good example of non-uniform type. Examples of the former include, un-doped [28] and doped graphene [29,30], MXenes [8,9,31,32] and the industry standard indium tin oxide, ITO. While the combination of transparency and conductivity of ITO is in general difficult to surpass, the high cost and limited supply of indium have energized efforts, especially in the 2D community, to find alternatives.…”

Li intercalation in graphite: A van der Waals density-functional study

“…Alkali, alkalineearth, or rare-earth-metal atoms can be inserted between the graphene layers of graphite without disrupting the bonding pattern within the graphene layers, and the electronic structure of the metal-graphite compound can be deduced from the interactions between the graphene and the metal layers [2,3]. Intercalation in few-layer graphene is explored for modifying its electronic, transport, and optical properties [4,5]. Some of these metal-graphite compounds even become superconducting [2,6,7].…”

“…Li x C 6 ; x < 0. 5 Whereas the structures of the fully lithiated stage 1 and stage 2 compounds are experimentally well established, less is known about the possible structures of Li x C 6 ; x < 0.5. As a first step, we have constructed a number of dilute stage 2 structures with compositions Li x C 6 , 1/8 x 1/2, and n×m in-plane Li lattices, √ 3 n,m 4.…”