The performance and the stability of PL dye-based DSSCs was investigated and compared with N719 dye-based DSSCs. The performance of the synthetic N719 dye-based DSSC achieved an efficiency
of 0.87%, whereas the highest efficiency recorded amongst the PL dye-based DSSCs was 0.28% at pH 3.5. The main variable contributing to this large difference in the measured efficiencies was the current density, which was determined not only by the LHE properties of the dyes but also by their –COOH functionalities and their HOMO–LUMO energy levels. Furthermore, the addition of
benzoic acid increased the acidity of the PL dyes up to pH 3.5, improving the performance of the DSSCs up to four times. The PL dye-based DSSCs with pH 3.5–4 displayed better stability than
the N719 dye-based ones. Further studies to improve the efficiency and stability of natural dye-based DSSCs could include the investigation of alternative dye extraction routes, such as isolating the pure chlorophyll from papaya leaves and stabilizing the pure chlorophyll.