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The National Centre for Photovoltaic Research and Education (NCPRE) at the Indian Institute of Technology Bombay (IITB) has developed a perovskite solar cell (PSC). The cell has been demonstrated an efficiency of over 26 per cent.
To compare, with the best of the conventional solar cells in the market, you will be lucky to get an efficiency of 22 per cent. Efficiency is the percentage of sun’s light energy that falls on the cell that is converted into electrical energy.
The authors, Prof Dinesh Kabra, et al, say that this cell could be “the gateway for the potential use in niche applications like building integrated photovoltaics (BIPV)”.
In material science, the word ‘perovskite’ refers to a certain crystal structure in which the atoms are arranged. It is in the form of ABX3. For example, Calcium titanium oxide, or CaTiO3 is a perovskite. Solar cells made with perovskite material are highly efficient at converting light into electricity. However, they are unstable and degenerate when exposed to light— or else the entire world would be using only perovskite solar cells (PSC) today.
Scientists the world over have been trying to get better efficiencies by marrying the perovskite cell to the conventional silicon cells. It is in this area of research that NCPRE has reported success. Their tandem structure has been found to be pretty stable.
“We have fabricated a stable 4T (four terminal) Si/perovskite tandem solar cells which provides outstanding stability in the dark as well as continuous heating conditions” say the authors in a recent scientific paper.
A 4T tandem device has four terminals — two for each of the layers of the tandem device. “This allows for precise measurements of the solar cell’s performance, while also improving the device’s efficiency and lifetime,” says a write-up on IIT-Bombay’s website.
A cell efficiency of 26 per cent, as reported by IIT Bombay, is perhaps a record. Recently, researchers at the National University of Singapore reported having achieved 24.35 per cent efficiency for a perovskite solar cell with an active area of 1 sq. cm.
However, it should be noted that when the cells are connected together to form a module—the panels that we see on rooftops — the efficiency will come down. The module efficiency under real-life conditions is the critical number. A Japanese start-up called EneCoat Technologies recently reported a module efficiency of 19.4 per cent, which is a very big number. Only further research will tell what the module efficiency of the NCPRE solar cell would be — if it exceeds even 20 per cent, it would be major news.
Perovskite solar cells have come a long way since the first cell was made in 2009. It had a conversion efficiency of 3.8 per cent.
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