A Double Support Layer for Facile Clean Transfer of 2D Materials for High-Performance Electronic and Optoelectronic Devices.

Clean transfer of 2D materials grown by chemical vapor deposition is critical for their application in electronics and optoelectronics. While rosin can be a support layer for the clean transfer of graphene grown on Cu, it has not been usable for the transfer of 2D materials grown on noble metals or for large-area transfer. Here, we report a poly(methyl methacrylate) (PMMA)/rosin double support layer that enables facile ultraclean transfer of large-area 2D materials grown on different metals. The bottom rosin layer ensures clean transfer, while the top PMMA layer not only screens the rosin from the transfer conditions but also improves the strength to make the transfer easier and more robust. We demonstrate the transfer of monolayer WSe and WS single crystals grown on Au as well as large-area graphene films grown on Cu. As a result of the clean surface, the transferred WSe retains the intrinsic optical properties of as-grown sample. Moreover, it does not require annealing to form good ohmic contacts with metal electrodes, enabling high-performance field effect transistors with mobility and ON/OFF ratio ~10 times higher than those made by PMMA-transferred WSe. The ultraclean graphene film is found to be a good anode for flexible organic photovoltaic cells with a high power conversion efficiency of ~6.4% achieved.