Ingenious process to cut down cost and complexity of crystalline silicon solar cell manufacturing process
Burning fossil fuel for energy has serious environmental impact. This is why the world is leaning toward photovoltaics. Over the years, parallel research approaches have given us two option to choose from: highly efficient solar cells or low-cost solar cells. This distinction is due to the complex manufacturing process required to make high-efficiency solar cell, thus limiting their outreach in society. Prof. Kottantharayil’s team at IITBNF have addressed this pivotal issue with an innovative solution.
A solar cell sequentially performs three fundamental tasks: it absorbs energy from sunlight, converts it into negative (electrons) and positive (holes) charge carriers, and finally, separately collects them at different electrical terminals. Solar cell efficiency depends on how effectively each of these three tasks is executed. Commercial, high-efficiency solar cells are made using completely flat, thin and very reflective pieces of silicon crystal. In order to increase light absorption, their front surface which faces the incident sunlight, is texturized. A texture consisting of tiny inverted pyramids is very effective to reduce reflection. These inverted pyramids are made using lithography, followed by selective removal of silicon by a chemical reaction. Complicated processes like these contribute significantly to the final cost of solar cell.
Mr. Saseendran, a PhD student from Prof. Kottantharayil’s group, while working on deposition of thin silicon nitride films on flat silicon surfaces, observed that these films blister and create local voids under certain process conditions. He derived a method to control the properties of these blisters and selectively remove silicon from the substrate underneath, through the voids. These experiments have led to the development of a low-cost alternative to expensive lithography process for fabrication of high-efficiency crystalline silicon solar cells.
Work funded/supported by: Ministry of New and Renewable Energy of the Government of India.
Published paper: Sandeep S. Saseendran and Anil Kottantharayil, “Inverted pyramidal texturing of silicon through blisters in silicon nitride” IEEE Journal of Photovoltaics, Vol. 5, No. 3, pp. 819 (2015).