The effect of nitrogen-doped carbon quantum dots for the application of dye-sensitized solar cells using Cu phthalocyanines as dyes

Two phthalocyanines were designed and used as sensitizers in dye-sensitized solar cells (DSSCs). These phthalocyanines bear p-coumaric acid as an electron-withdrawing and anchoring group, with bulky 4- [4-(1,1,3,3-tetra-methylbutyl phenoxy groups (CuPc1) and tert-butylphenoxy groups (CuPc2) as electron-donating groups. The impact of electron-donating groups on the energy conversion efficiency of solar cells was also studied. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the dyes were investigated using differential pulse voltammetry (DPV). Additionally, nitrogen-doped carbon quantum dots (N-CQDs) were prepared and used as a counter electrode and co-sensitizer. It was observed that CuPc1 achieved the maximum efficiency of 1.25%. Upon the addition of N-CQDs as a co-sensitizer, the maximum efficiency was 1.69% with CuPc1 as the sensitizer.