Theoretical insights on the comparison of champion dyes SM315 and C275 used for DSSCs reaching over 12% efficiency and the further optimization of C275

Abstract Theoretical insights on the comparison between the champion dyes SM315 and C275 used for high-performance dye-sensitized solar cells (DSSCs) reaching over 12% efficiency with different electron donors only (porphyrin for SM315 and indenoperylene for C275 ) were explored for the first time. The intrinsic reasons for the significantly improved monochromatic photon-to-electric current conversion efficiency ( IPCE ) and open circuit voltage ( V oc ) of C275 -based DSSCs over those of SM315 were revealed. According to our results, we find that the larger IPCE of C275 is attributed to its larger electronic coupling, smaller reorganization energy, reduced exciton binding energy and enhanced charge transfer character, all of which when combined lead to a larger electron injection efficiency. In addition, the larger V oc of C275 is due to a greater number of injected electrons, a smaller molecular volume and a smaller projected area, which lead to a more compact adsorption layer with a hindered charge recombination process. Thus, C275 is expected to have more potential to further optimize high-performance DSSCs. In view of the primary shortcoming of C275 , which is its relatively narrow absorption spectrum, further optimization was made through structural modification using a series of heterocyclic anchoring groups. Using the same evaluation criteria, the theoretical screening of these dyes based on C275 is carried out. We find that indenoperylene dye with a barbituric acid ( BA ) anchoring group is a promising candidate for the experimental synthesis of high-performance DSSCs with improved J sc , V oc and adsorption stability.