IIT-H researchers improve efficiency of third gen solar cells

Hyderabad: Indian Institute of Technology Hyderabad researchers have developed a novel process to improve the performance of third generation solar cells. Working with Dye Sensitized Solar Cells (DSSC), they have shown that the incorporation of magnetic nanoparticles (Fe3O4) in the anode can enhance light-to-power conversion efficiencies. Their most recent work has been published in the journal Solar Energy, a peer-reviewed journal.

There is much promise for dye sensitised solar cells because of cost and environmental benefits possible and it is expected that with improvements in performance, DSSCs could outdo mature silicon based solar cells. The worldwide DSSC market is projected to reach $60 million by 2023, but such a market can be tapped only with efficiency improvements. Research such as those of the IITH team can contribute towards global efforts to bring DSSCs into real-life applications.

The research is being headed by Dr Jammalamadaka Suryanarayana, Associate Professor, Magnetic Materials and Device Physics Laboratory, Department of Physics, IIT Hyderabad, with his student Kannan U M in collaboration with Dr. L. Giribabu, senior scientist, Indian Institute of Chemical Technology, Hyderabad.

Speaking about his research, Dr Suryanarayana said, "Photovoltaic or solar cell technology has been around since 19th century and we are now seeing third generation of cells. The first-generation silicon-based cells, with energy harvesting efficiency of about 26%, continues to be costly. Second-generation thin film solar cells based on semiconductors like CdTe and CdSe have comparable efficiencies, and not much lower cost. The third generation of Dye Sensitized Solar Cells (DSSCs) can significantly lower costs of solar cells while being environmentally friendlier than earlier generations, but their efficiencies need improvement to translate to practical products."

The efficiency of these cells, also known in the scientific community as 'the Grätzel cell,' after its inventor Michael Grätzel, continues to hover around 13 per cent and there is considerable research all over the world to improve its performance.

Dr. Suryanarayana's Research Team at IIT Hyderabad used a unique approach to improve the output of the DSSC. "In simplistic terms, a dye molecule (N719) absorbs the light energy in DSSC and causes electrons in the dye to jump to titania and then to the external circuit, which causes a flow of electrons, leading to a current", he explained.

The introduction of Holmium oxide (Ho2O3), a powerful paramagnetic material, into the anode of the cell resulted in an enhancement in the power conversion efficiency. In addition, it has been long known that the motion of electrons is affected by magnetic fields and application of such fields can influence the trajectory of electrons in the device. To test this idea, the research team applied external magnetic fields to the solar cell and noticed that there were significant improvements in the output.

Although the application of external magnetic field in combination with Ho2O3 gave an enhancement, it can be parasitic because electromagnets themselves require energy for their functioning. In their next phase of research, the research team added magnetic nanoparticles (iron oxide) to the anode, instead of paramagnetic Ho2O3, in order to utilize the internal magnetic field produced by these particles.

Since it was highly challenging to experimentally determine the contribution from the internal magnetic field once the device was fabricated, the researchers used magnetic force microscopy (MFM) and micromagnetic simulations to quantify the magnetic field arising from the addition of the iron oxide nanoparticles. Experimental evaluation of these modified DSSC showed that there was a substantial enhancement in the power conversion efficiency.