title: 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 Ω per square is achieved for 19-layer LiC6, which corresponds to a figure of merit σ(dc)/σ(opt) = 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.
authors: 1] Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA [2] Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-4111, USA [3] University of Maryland Energy Research Center, College Park, Maryland 20742-4111, USA [4].
authors: Wenzhong
authors: W
authors: Bao
authors: 1] Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-4111, USA [2] University of Maryland Energy Research Center, College Park, Maryland 20742-4111, USA [3].
authors: Jiayu
authors: J
authors: Wan
authors: 1] Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-4111, USA [2] University of Maryland Energy Research Center, College Park, Maryland 20742-4111, USA.
authors: Xiaogang
authors: X
authors: Han
authors: Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors: Xinghan
authors: X
authors: Cai
authors: 1] Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-4111, USA [2] University of Maryland Energy Research Center, College Park, Maryland 20742-4111, USA.
authors: Hongli
authors: H
authors: Zhu
authors: Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors: Dohun
authors: D
authors: Kim
authors: 1] Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742-4111, USA [2] Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors: Dakang
authors: D
authors: Ma
authors: 1] Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742-4111, USA [2] Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors: Yunlu
authors: Y
authors: Xu
authors: 1] Department of Electrical and Computer Engineering, University of Maryland, College Park, Maryland 20742-4111, USA [2] Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors: Jeremy N
authors: JN
authors: Munday
authors: Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA.
authors: H Dennis
authors: HD
authors: Drew
authors: 1] Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA [2] School of Physics, Monash University, Melbourne, Victoria 3800, Australia.
authors: Michael S
authors: MS
authors: Fuhrer
authors: 1] Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-4111, USA [2] University of Maryland Energy Research Center, College Park, Maryland 20742-4111, USA.
authors: Liangbing
authors: L
authors: Hu