In this work, we demonstrate that graphene films synthesized by chemical vapor deposition (CVD) method can be used as thin transparent electrodes with tunable work function. By immersing the CVD-grown graphene films into AuCl₃ solution, Au particles were formed on the surface of graphene films by spontaneous reduction of metal ions. The surface potential of graphene films can be adjusted (by up to ∼0.5 eV) by controlling the immersion time. Photovoltaic devices based on n-type silicon interfacing with graphene films were fabricated to demonstrate the benefit of an electrode with tunable work function. The maximum power conversion efficiency (PCE) achieved was ∼0.08%, which is more than 40 times larger than the devices without chemical doping.