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 AuCl(3) 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 approximately 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 approximately 0.08%, which is more than 40 times larger than the devices without chemical doping.