Dye-Anchored Nanocatalysts for Improved Solar Energy Conversion Efficiency in Dye-Sensitized Solar Cells

With the demand for renewable and environmental friendly energy source, solar cell devices as an emerging technology, which can directly convert solar energy into electrical power with the least environmental impact, have played an important role in helping the nation reduce the growth of its carbon dioxide emissions in the long term. The most commonly researched types of solar cells were the crystalline silicon solar cells since the early 20th century. They were generally very efficient but costly and difficult to produce since the silicon materials should be high purity in order to achieve a high efficiency. Therefore, researchers developed the cheaper but less efficient thin-film cells, dye-sensitized solar cells (DSSCs). DSSCs are a very promising technology due to their attractiveness as cost-effective alternatives to conventional silicon-based photovoltaic devices.

In the DSSCs, the dye is left oxidized after photo injecting an electron. A redox couple usually comprised of iodide/triiodide (I–/I3–) in the electrolyte regenerates the oxidized dye to its neutral state and carries the positive charge to the platinized counter-electrode. On the counter electrode, I3- will be reduced to I- and complete the circuit. I–/I3– has been commonly used as the redox couple due to its high ion mobility and slow recombination of electrons from TiO2 to the oxidized species, I3–. However, the regeneration of oxidized dye by I– is not a simple one step reaction, which causes a large voltage loss of about 0.5–0.6 V due to the formation of diiodide radicals (I2–•). In this work, Pt nanoparticles have been prepared as the localized catalyst for the dye regeneration. A new dye molecule (AK1) with dithiolane groups was synthesized for the binding to Pt nanoparticles and the TiO2–dye–Pt system was assembled.

In summary, the developed methods for the preparation of Pt nanoparticles and systematically comparison of different agent effects will open up new avenues in the preparation of noble metal based nanomaterials and can be potentially extended to the synthesis of a wider range of electrocatalysts and photocatalysts in the application of DSSCs. The rationally designed new dye molecule was synthesized and applied to the binding with Pt nanoparticles to demonstrate the proof-of-concept of using Pt nanoparticles to catalyze the regeneration of dye by I– to reduce the overpotential hence improve the performance of DSSCs.