Researchers from IIT Roorkee and CSIR-NCL Pune together developed organic dyes that can increase efficiency of Dye-Sensitised Solar Cells (DSSC). A research team led by Dr. M. Sankar, Associate Professor, Dept. of Chemistry, IIT Roorkee came up with a way to improve the photovoltaic conversion efficiencies of an organic dye called ‘porphyrin’ for DSSC applications, post rigorous research work. Remarkably, American Chemical Society (ACS) called ACS Applied Energy Materials published the research results in their journal.

It was back in 1993, the first study on the use of porphyrins, a complex organic molecule that allows plants to harvest light energy for photosynthesis was conducted and it resulted in power conversion efficiencies of 2.6 percent, too low for practical applications. Later, several modifications were done on porphyrins and finally Zinc containing porphyrins have been found promising and the research team at IIT Roorkee used this for their studies. However, solar cell technologies fall into three generations and the first and second generations uses inorganic semiconducting materials such as single crystal silicon (Gen I) and thin film silicon and CdSe type semiconductors (Gen II). Third generation which is still in research stage includes DSSC, uses a combination of cheap organic dyes and nanoparticles of titanium dioxide, to convert light into electricity.

Commenting on the research, Dr. Sankar, says, “Our continuous efforts to develop simple, efficient, stable, and cost-effective sensitizers involving fewer synthetic steps have resulted in five porphyrin Zn(II) complexes with a power conversion efficiency ranging from 5.3 percent to 7.1 percent. We have also showed the scalability of the synthetic approach”.

Globally, aggressive research on improving the light-to-energy conversion efficiencies of DSSC has made it a competitor to first and second generation solar cells. Adding molecular pendants or groups to it will increase the shuttle of electrons released in the molecule. This leads to the absorption of light in the red and infrared regions, increasing the the efficiency of the dye in photo-electric conversions. Using Density Functional Theory (DFT) calculations, researchers were able to study the electron density distribution in frontier molecular orbitals (FMOs) and for geometry optimization. Researchers also studied the photo-electric properties of the dyes by standard methods such as optical and fluorescence spectroscopy, cyclic voltammetry, impedance spectroscopy and PV measurements, and all showed improved performance of the dyes.

Established in 1847, IIT Roorkee is an institute of national importance in imparting higher education in engineering, sciences, management architecture and planning. It was converted to IIT Roorkee in 2011 and it has played a vital role in providing technical manpower to the country.

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