Observing Electron Extraction by Mono layer Graphene Using Time-Resolved Surface Photoresponse Measurements
|Title||Observing Electron Extraction by Mono layer Graphene Using Time-Resolved Surface Photoresponse Measurements|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Zhang, LS, Roy, SS, English, CR, Hamers, RJ, Arnold, MS, Andrew, TL|
|Keywords||anodes, built-in, charge extraction, chemical-vapor-deposition, films, GRAPHENE, heterostructures, interface, organic solar-cells, pentacene, photovoltaics, substrate, surface photoresponse, voltage|
Graphene is considered a next-generation electrode for indium tin oxide (ITO)-free organic photovoltaic devices (OPVs). However, to date, limited numbers of OPVs containing surface-Modified graphene electrodes perform as well as ITO-based counterparts, and no devices containing a bare graphene electrode have been reported to yield satisfactory rectification characteristics. In this report, we provide experimental data to learn why. Time-resolved surface photoresponse, measurements on templated pentacene-on-graphene films directly reveal that p-doped monolayer graphene efficiently extracts electrons, not holes, from photo-excited pentacene. Accordingly, a graphene/pentacene/MoO3 heterojunction displays a large surface photoresponse and, by inference, efficient dissociation of photogenerated excitons, with graphene serving as an electron extraction layer and MoO3 as a hole extraction layer. In Contrast, a graphene/pentatehe/C-60 heterojunction yields a comparatively insignificant surface photoresponse because both graphene and C-60 act as competing electron extraction layers. The data presented herein:provide experimental insight for future endeavors involving bare graphene as an electrode for organic,photovoltaic devices and strongly suggest that p-doped graphene is best considered a cathode for OPVs.
|URL||<Go to ISI>://WOS:000351791800027|