Molecular design of porphyrin dyes for dye sensitized solar cells: A quantitative structure property relationship study

Porphyrins dyes are known as promising sensitizers for dye sensitized solar cell (DSC) devices because of their intrinsic features with maximum reported light-to-electricity conversion efficiency of about 12%. Our objective in this study is to rationally design new porphyin sensitizers with enhanced photovoltaic (PV) properties, V_oc (open-circuit voltage), or J_sc (short-circuit current density) for DSC applications. We have used quantitative structure-property relationship technique following a heuristic approach to build a structure-property (PV) relationship on a dataset of 45 experimentally reported push-pull Zn-porphyrin based sensitizers. The model is further used to predict PV properties; V_oc and J_sc of 71 new structures. The model includes a unique combination of constitutional, topological, and electrostatic descriptors along with the widely used quantum chemical descriptors to establish a structure-property relationship. The results furnished guide-in principles in identifying 8 structures as potential candidates based on their frontier molecular orbital energies, absorption in visible-near IR region (extending up to 900 nm), reorganization energies, in addition to favorable PV properties. In conclusion, the study has demonstrated how a subtle variation in porphyrin structure particularly of the auxiliary groups can be used to modulate their PV properties.