Nitrogen-containing carbon dots were applied to improve the performance of phthalocyanine-sensitized solar cells. Nitrogen-doped carbon dots were prepared by carbonizing the citric acid as a carbon source in water due to their green and environmental friendliness properties. Two sets of dye systems consisting of phthalocyanine-carbon dots conjugates and phthalocyanine-doped carbon dots have been provided to elucidate the influence of nitrogen-doped carbon dots on the performance of devices. The synthesis of phthalocyanines and derived metal complexes was done using the controlled microwave heating method as a green procedure. The good biocompatibility and excellent water solubility of citric acid-based carbon dots in combination with green manufacturing of phthalocyanines make the prepared dye systems appropriate to be used as green sensitizing systems in solar cells. The phthalocyanine-carbon dots conjugate systems were prepared by mixing the related phthalocyanines and nitrogen-doped carbon dots, while the phthalocyanine-doped carbon dots were prepared by in situ synthesis of nitrogen-doped carbon dots in the presence of the related phthalocyanines. Metal-free phthalocyanines and metal-ophthalocyanines (metal: manganese, iron, cobalt, nickel, copper, and zinc) were prepared and examined to show the effect of the metal in the core of phthalocyanine on the performance of devices. Also, un-substituted and carboxyl-and sulfo-substituted derivatives of phthalocyanines were studied in both sets of dye systems. The obtained results confirmed the significant influence of nitrogen-containing carbon dots on the performance of the solar cells. (C) Published by Elsevier Ltd.