Hafnium (IV) and zirconium (IV) porphyrinoid diacetate complexes as new dyes for solar cells

New concepts in the design and function of organic dyes as sensitizers for solar energy harvesting are needed. Simple porphyrin dyes offer cost effective synthesis and long-term stability, but new modes of incorporation into devices are needed to increase the efficiency of charge separation that drives any photonic device designed to harvest light. We are developing a new strategy to couple dyes to oxide surfaces using hafnium and zirconium metalloporphyrins. The formation of ternary complexes of Hf(IV) and Zr(IV) porphyrins with a Keggin polyoxometalate (POM), PW₁₁O^7-₃₉ suggested that one way to self-organize porphyrinoids onto oxide surfaces is to use oxophilic group IV metals Hf and Zr. The 3-4 open metal coordination sites of Hf(Por) ²⁺ and Zr(Por)²⁺ are bound primarily to surface defect sites by displacement of the auxiliary acetate ligands.