In solar cell technology field, a Pakistani scientist has established two world records.

In the lab, a team led by Pakistani scientists produced a promising solar cell technique that broke two world records for efficiency. The strategy might aid in the development of clean energy programs to counteract global warming.

Yasir Siddique, a PhD student at the Korea Institute of Energy Research (KIER) and the Daejeon University of Science and Technology (UST), has developed and manufactured solution-processed Copper Indium Sulphu Selenide (CISSe) solar cells.

The stable solution-processed, low bandgap CISSe device works flawlessly as a single cell, but it may also be sandwiched with other thin-film solar cell materials with sufficient bandgap as the top cell, such as Perovskite, a recently developed solar cell technology.

Our sun is 150 million kilometres away on average, but it is the major source of light and heat for our world. The sun, in theory, radiates 1,360 watts per square metre of combined energy onto a surface facing it.

However, the majority of sunlight on every solar cell is reflected or transmitted through the structure, and only a small percentage of that energy is converted directly into electricity. So, the efficiency, or the degree to which a solar cell transforms energy from sunrays, is the power conversion rate.

Solar cells come in a variety of shapes and sizes, each with a different efficiency. Another way to characterise them is as the first, second, and third generation of solar cells. Traditional silicon cells have efficiencies of 15 to 20%, but concentrated solar cells reach efficiencies of 41% but require focussed beams at a single location.

Siddique's cell, on the other hand, is part of the growing Tandem solar technology trend and is now the most efficient in its category.

Siddique’s recent innovation took three years to develop and finally the CISSe only cell allows the efficiency of 14.4 per cent when it is blended with perovskite (perovskite/CISSe) cell touched the efficiency of 23.03 per cent. This is the highest efficiency as compared to all solution-processed (perovskite/CISSe) solar cell category.

The solar cell's recipe

A team of Chinese, Americans, and Australians set the previous record with a 13.5 percent efficiency of the same sort of solar cells. However, the production of such cells was limited to a glass-based glove box filled with nitrogen gas. In order to mass produce, a large amount of nitrogen was required, making commercialization practically impossible.

Later, the KIER team proposed a method to control and obtain an optimal degree of crystallisation of the precursor layer by using air annealing temperature – a common heating and cooling method used in electronics – not only to remove carbon contents in the cell's absorber film but also to remove carbon contents in the cell's absorber film. Perfect crystallisation is essential for achieving the desired outcomes.

In electronics manufacture, air annealing is used to improve physical, optical, and structural characteristics. Heat treatment of steel, for example, is a standard method for making the metal more ductile.

Four precise samples were annealed in the air at temperatures of 210, 230, 280, and 330 degrees Celsius. 230°C was discovered to be the best air annealing temperature in experiments, and it was at this temperature that they were able to build a CISSe solar cell device with a verified world record efficiency of 14.4%.

A thin perovskite solar cell was then put on top of the CISSe cell for additional investigation. This double-layered, all-solution processed perovskite/CISSe tandem solar cell achieves a world record efficiency of 23.03 percent, which is also a world record in this category of solar cells.

Perovskite is a potential material for carving effective solar cells that was discovered in the 1800s by Russian scientists, and Siddique enhanced this by adding the CISSe device.