We report the use of triethylenetetramine (TETA) as a dopant of graphene transparent conducting electrodes (TCEs) for Si heterojunction solar cells. The molar concentration (n(D)) of TETA is varied from 0.05 to 0.3 mM to optimize the graphene TCEs. The TETA-doped graphene/Si Schottky solar cells show a maximum power-conversion efficiency (PCE) of 4.32% at n(D) = 0.2 mM, resulting from the enhanced electrical and optical properties, as proved from the n(D)-dependent behaviors of sheet resistance, transmittance, reflectance, series resistance, and external quantum efficiency. In addition, polymethylmethacrylate is employed as an antireflection layer to enhance the light-trapping effect on graphene/Si solar cells, resulting in further enhancement of the maximum PCE from 4.32 to 5.48%. The loss of the PCE is only within 2% of its original value during 10 days in air. (C) 2017 Elsevier B.V. All rights reserved.