Compared to traditional silicon based solar cells, dye-sensitized solar cells, or Graetzel cells, have significantly lower production costs, even though the former still show higher efficiency. Nevertheless, due to additional sustainable features such us easy availability and environmental friendliness, dye-sensitized solar cells (DSSCs) have attracted attention among the worldwide research community. A research team from Amrita School of Biotechnology (ASB) is joining this global community.

As a consequence of such research activities, improvements in the efficiency of DSSCs are expected in the future. Experts predict that the correspondent scientific breakthrough will replace traditional solar cells.

Dr. C. O. Sreekala, Assistant Professor and Jinchu I., Research Associate, of Amrita School of Biotechnology, are heading a research team, engaged in tailoring the efficiency of dye sensitized solar cells.

Trans Tech Publications recently published three of their papers in the specific area of “Potential Development in Natural Dye-Sensitized Solar Cells for Renewable Energy.” The papers were also co-authored by, K. S. Sreelatha, Govt. College of Kottayam, Dr. Krishnashree Achutan, Chairman, Center for Cyber Security, Amrita Vishwa vidyapeetham, P. F. Saneesh, Technical Manager, Virtual Labs, and M. S. Roy, Defense Laboratory, Jodhpur.

Briefly summarized, DSSC technology imitates the mechanism of photosynthesis by which plants convert sunlight into energy. Instead of chlorophyll, a light absorbing dye is used. Exposure to light causes a higher energy state in the dye molecule, which is captured by surrounding catalyst and electrolytes.

The review paper titled “Dye Sensitized Solar Cell (DSSC) using Natural Dyes as Chromophores” compares the efficiency of different natural dyes.

“The most successful dyes are based on ruthenium bipyridyl compounds. Ru containing compounds absorbed on nanocristalline titanium dioxide Ti O2 reached 11-12% efficiency rate,” the researchers share.

“However, the noble metal ruthenium base is limited and therefore expensive. Organic dyes which have also reached efficiency as high as 9.8% can be extracted by simple procedures from fruits and flowers are more economic and environmentally friendly”, they added.

“The best performance was noted for betalain pigments. Hence, it can be concluded that the interaction between betalain and TiO2 is high. Curcumin, Cyanin, Shisonin, Clorophyll and Malaonyshisamin also formed better bonds with TiO2 compared with other plant pigments,” the team concludes.

The team further performed various experiments to test the photovoltaic performance of DSSC using natural dye with the surface modification of the photo anode and presented the result in their paper titled “Enhanced Photovoltaic Performance of the Dye Sensitized Solar Cell Using Natural Dyes with Surface Modification of the Photo anode”.

The good light harvesting property of the photo anode indeed determines the efficiency of a dye sensitized solar cell.

“We used Lawsone (2 hydroxyl [1, 4] -naphthoquinone), the natural dye and compared the performance of photo anode in bare TiO2 and with nonporous CaCO3 coated TiO2. As compared to bare TiO2, the surface area of nonporous CaCO3-coated TiO2 increased, consequently, a better amount of dye adsorption occurred. The coating of CaCO3 increased the impedance at TiO2/dye/electrolyte interface and affected lifetime of the photoelectrons. Due to this reasons the short circuit current Jsc, open-circuit voltage and fill factor increased, thus the energy conversion efficiency of the solar cell has improved,” Dr. Sreekala explained.

“Organic Bulk Heterojunction Solar Cell Based on Rosebengal: ncTiO2 and Parameter Extraction by Simulation” is the title of the third paper.

Abstracts of the papers can be accessed at http://www.scientific.net, the E-publisher of Trans Tech Publications.

October 3, 2013
School of Biotechnology, Amritapuri