Biomimetic solar cells

Paper presented to the 6th Annual Symposium on Graduate Research and Scholarly Projects (GRASP) held at the Hughes Metropolitan Complex, Wichita State University, April 23, 2010.Research completed at the Department of Chemistry, College of Liberal Arts and SciencesEco friendly energy resources are becoming important due to the predicted oil depletion and soared CO₂ emission. Of available alternatives, solar energy finds special attention due to its vast availability and high power density of 1000 watts per square meter. Various mechanisms have been carefully employed to harvest the solar power including semiconductor silicon based photovoltaic, inorganic/organic dye sensitized or bulk hetero junction solar devices. Some of the latter devices utilize donor-acceptor supramolecular systems designed based on natural photosynthesis. Here, self-assembly of energy donor and acceptor are proved to be an important criterion.In the present study, we demonstrate an elegant method of self-assembly to modify TiO₂ surface using coordinating ligands followed by immobilization of a variety of photosensitizers and dyads. In this method, in addition of testing the photoelectrochemical behavior of different zinc tetrapyrroles, it also allowed us to introduce fairly complex structures involving more than one donor entities. Of all macrocycles studied, zinc porphyrin-ferrocene dyad markedly improved the current-voltage performance of the photoelectrochemical cell due to an electron transfer-hole migration mechanism. Incident photon-to-current efficiency values up to 37%, highest values ever reported for this type of electrodes was obtained for the electrode modified with the dyad, highlighting the importance of photocells built based on biomimetic principles for efficient harvesting of solar energy