Effects of gold nanoparticles dispersed in anodes for dye sensitized solar cells

Abstract

Future solar cells need to be cheaper, more efficient and produced in an environmental friendly way to be a competitive and sustainable alternative for solar energy conversion. The emerging dye sensitized solar cells (DSSCs) might be able to meet future demands regarding price, structural flexibility and environmental issues, but for the time being, their potential as a competitive and viable alternative is hampered by low energy conversion efficiencies and stability issues. A most central process in the conversion of sunlight energy directly into electric energy, is the photon to charge carrier conversion which takes place in the photoactive part of the solarcell. To achieve a high incident photon to charge carrier efficiency (IPCE), efficient absorption of incoming sunlight over a wide range of wavelenghts is needed. The use of plasmonic effects generated by metal nanoparticles (MNP) in combination with a sensitizing dye is an interesting approach to increase the IPCE for DSSCs. In this work, effects on cell energy conversion efficiency of adding gold nanoparticles (GNPs) have been studied. Spherical GNPs of diameter 5, 10 and 40 nm, embedded in the photoactive layers have been studied in combination with three different sensitizing dyes; Ruthenizer 455-PF6, Ruthenizer 620-1H3BTA and Sensidizer SQ2. Cells without dye were also included in the study. TiO2 was used as semiconductor material in thin(< 1μm ) photoactive layers. Complete DSSCs containing gel electrolyte have been built and characterized with I-V graphs using different light intensities of 0.11, 0.55, 0.79 and 1.0 sun. The results clearly show that the cell efficiency can be improved by using GNPs this way, it was also shown that certain combinations of dye and GNP sizes affected cell efficiency more positive than others while addition of GNPs to cells without dye sensitizer affected the efficiency negatively. Most positive results were achieved using the organic dye Ruthenizer 455-PF6 in combination with 40 nm GNPs, showing relative efficiency increase well above 25 %.