Over the years, thanks to the devoted research work going on for increasing the efficiency of solar cells, today solar cells are no longer flat shaped or unyielding. Ultra thin film-type solar cells have now been manufactured which are quite flexible and adaptable for use in corners, curvilinear and other structures. Today almost 20% of global solar power generation is done by these thin-film solar cells and expected to grow more in near future.
Increasing the efficiency of thin-film solar cells
The films when assembled into an array are only as efficient as the ‘microchannels’ on the films which help convert the sunlight to electrons needed for power generation. Until now the ’scribing’ of the microchannels have been done with the help of a mechanical stylus which is an expensive process. Also the channels so produced are not perfect with exact grooves or uniform depth. Now the new research has developed a way to do channel scribing with the help of lasers.
Laser scribing made easy
The research team focused on ways to improve the scribing of the microchannels. Better the microchannels, more efficient will be the solar cells. They tried a process called ‘cold ablation’ to use laser beams flashed for only picoseconds – quadrillionths of a second. This way, pulsing laser helped in making microchannels with exact depths and well-defined outlines without causing any damage to the ultra-thin-film solar cells and too in a very fast manner.
Superiority of the ‘ultrashort pulse laser’
The idea of using lasers for scribing the microchannels on the thin-film solar cells has been tried earlier also. But controlling the lasers to scribe exactly to the correct depth and outline was quite a difficult task. But now with the cold ablation technique and using an ‘ultrashort pulse laser’, the team found success in creating perfect microchannels. With this technique, the team was able to control the laser even at 10-20 nanometer depth.
Success of the team
The team is hoping to improve the efficiency of the thin-film solar cells and also reduce the cost factor. ‘Ultra-short pulse laser, ultrafast laser scribing’ & ‘cold ablation technique’ will improve the efficiency of the cells, and commercial production will be hugely benefited with this. As Professor Yung Shin puts it, “The efficiency of solar cells depends largely on how accurate your scribing of microchannels is… If they are made as accurately as possibly, efficiency goes up.”
The research team
The research team consists of Yung Shin, Professor of Mechanical Engineering & Director of Purdue University’s Center for Laser-Based Manufacturing, and Gary Cheng, Associate Professor of Industrial Engineering and Martin Yi Zhang, Seunghyun Lee and Wenqian Hu – graduate students. They published a paper in Proceedings of the 2011 NSF Engineering Research and Innovation Conference this January. The research has been funded by National Science Foundation with a $425,000 grant for three years.
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