Charge transfer doping is a renowned route to modify the electrical and electronic properties of graphene. Understanding the stability of potentially important charge-transfer materials for graphene doping is a crucial first step. Here we present a systematic comparison on the doping efficiency and stability of single layer graphene using molybdenum trioxide (MoO3), gold chloride (AuCl3), and bis(trifluoromethanesulfonyl)amide (TFSA). Chemical dopants proved to be very effective, but MoO3 offers better thermal stability and device fabrication compatibility, Single layer graphene films with sheet resistance values between 100 and 200 ohm/square were consistently produced by implementing a two-step growth followed by doping without compromising the optical transmittance. (C) 2017 Elsevier B.V. All rights reserved.