New Class of Pt Complexes for Solar Cells

Author: Sarah Millar
Published On: February 26, 2014
Source/Publisher: Chemistry – A European Journal/Wiley-VCH
Copyright: Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Tremendous progress has been made in the development of solar cells based on panchromatic ruthenium dyes. The most efficient photosensitizer, the Ru^II polypyridine complex, achieves up to 11.4 % efficiency. However, one of the disadvantages of using Ru complexes is their limited absorption in the visible region. Thus, the hunt continues for new materials that can enhance the light absorption capability in this region and so enhance the overall efficiency.

Vivian Yam and co-workers, University of Hong Kong, China, have created a new class of molecular dyads comprising metalloporphyrin-linked alkynylplatinum(II) polypyridine complexes with carboxylic acids as anchoring groups. These complexes undergo charge transfer from the alkynylplatinum(II) terpyridine units to the metalloporphyrin units, giving them interesting electronic absorption and redox properties. UV/Vis absorption studies indicated that all of the complexes displayed intense absorptions in the high-energy region, more-intense absorption bands at about 420–450 nm, and less-intense absorptions in the low-energy region. All of the complexes could sensitize a nanocrystalline TiO₂ electrode efficiently, as revealed by the excited-state redox potentials. These showed that the complexes were able to inject an electron into the conduction band of TiO₂.

A dye-sensitized solar cell (DSSC) based on the best complex showed a short-circuit photocurrent of 10.1 mAcm^–2, an open-circuit voltage of 0.64 V, and a fill factor of 0.52, giving an overall power conversion efficiency of 3.4 %. Although this value is not comparable with the Ru^II polypyridine complex, the team believes that this class of complexes may inspire new donor-acceptor metal-ligand chromophores and photosensitizers with improved properties.