The main purpose of this work is to explore the effect of graphene quantum dots (GR) filling the photosensitive layer. The multibranched dye JH-1 as the photoactive layer material was used to analyze the non-negligible role of graphene quantum dots from the perspectives of optimized structure, electrochemical parameters, optical properties, nonlinear optical (NLO) switch, and external electric field. The results demonstrated that the graphene quantum dots not only improve the optical properties of solar cells but also control the electron transfer in the photosensitive layer molecules under the manipulation of a specific external electric field. When the external electric field intensity is below 20 x 10(-4) au, the excess electron orbital does not change. When the external electric field reaches 25 x 10(-4) au, the excess electron orbital on the graphene quantum dots evolves. This discovery allows the electron transfer from the photosensitive layer, which should be controlled by the NLO switch. In addition, the optical properties of sensitizers showed regular evolution in the external electric field, which provides an effective way to improve the performance. Comprehensive analysis indicated that the doping of graphene quantum dots with the photosensitive layer can be used as a new way to improve the photoelectric conversion efficiency of solar cells.