Abstract A comprehensive prediction for molecular power conversion efficiency and designing novel sensitizers are effective strategies for preparing highly efficient dye-sensitized solar cell devices. In this work, four high-efficiency D-π-A type triazatruxene (TAT) based organic dyes have been designed by changing spacers and anchoring groups of the reference molecule. A global evaluating model that illustrates the micro-mechanism of enhanced molecular photoelectric performances through importing graphene quantum dots (GQDs) was built. Upon incorporating GQDs, an obvious absorption peak with high molar extinction coefficients appeared around the ultraviolet region. Furthermore, molecular light-harvesting efficiency (LHE) in the visible region has increased, and molecular charge transfer performance enhanced, and molecular regeneration ability improved, which contributed to the improved photocurrent (Jsc) and power conversion efficiency (PCE). Molecular ZL003 through the global evaluating model showed (Jsc = 19.03 mA cm−2, Voc = 0.874 V, PCE = 14.5%) are in accordance with the experimental data (Jsc = 19.74 mA cm−2, Voc = 0.957 V, PCE = 13.4%). The model can provide a basis for evaluating molecular photoelectric performance. The micro-mechanism that the GQDs enhance molecular photoelectric performances has been revealed in the framework of GQDs photo current-voltage evaluating model.