Metal and nitrogen co‐doped carbon dots in the sensitized solar cells

Abstract

Doped carbon dots are used to upgrade the efficiency of the porphyrin‐sensitized solar cells (PSSCs). Nitrogen‐doped carbon dots (NCDs) and metal and nitrogen co‐doped carbon dots ([M]NCDs; M: manganese, iron, cobalt, nickel, copper, and zinc) are applied in the PSSCs structure to improve the performance. Study on the substituted porphyrins is showing the effect of the substitutions of the porphyrins on the performance of PSSCs in the presence of NCDs as co‐sensitizer. The ZnTCPP/NCDs has made the biggest impact on the performance of the solar cell relative to other porphyrins; increase from 0.76% to 1.84% in PCE (power conversion efficiency) relative to ZnTPP/NCDs can be seen. The results that are related to the use of NCDs and (M)NCDs as co‐sensitizer are showing the impact of impurity doping in CDs on the PSSCs' efficiency. In the case of doped CDs in the presence of ZnTCPP, the performance of PSSCs using (Ni)NCDs and (Zn)NCDs is showing more increase relative to the use of other prepared carbon dots as co‐sensitizer. PCE of the solar cells sensitized by ZnTCPP/(Ni)NCDs and ZnTCPP/(Zn)NCDs was increased from 1.10% to 2.75% and 3.09%, respectively, in comparison with only ZnTCPP. Based on computational results, the Zn2+ and Ni2+ are playing a direct role on the highest occupied molecular orbital (HOMO) and (lowest unoccupied molecular orbital) LUMO of (Zn)NCDs and (Ni)NCDs, respectively. Also, based on the partial density of states analysis, the metal ions such as Zn2+ and Ni2+ in the (Zn)NCDs and (Ni)NCDs, respectively, are playing an important role in HOMO and LUMO of investigated systems, and these two metals have high amount of contributions in the mentioned levels.