Whenever I overhear conversations on the environment, the common consensus is always, “why don’t they just put solar panels everywhere?” As much as that would be the most optimistic scenario, there have been and still are some serious road blocks to widespread solar panel use: efficiency and cost.
The theory of lowering cost is easy. Increase production efficiency, and panel cost will lower — this is mostly straightforward, but of course, takes some time. Increasing solar efficiency (the amount of the sun’s photons that convert to electrical energy) doesn’t have such a straight forward process.
Nonetheless, humans have prevailed and it seems a few scientists at Purdue University have completed some research to improve both the cell and production efficiencies of solar panels. By using lasers to scribe microchannels in the cells, the researchers were able to improve the efficiency of inter-cell power transfer, thereby increasing overall efficiency of multi-cell thin-film solar cells.
Current solar panels are made in ways not dissimilar to microprocessor production: evaporating metals onto semiconductor substrates. The Purdue research found that cell-interconnects, made of the evaporated metals, were found to be a large source of energy loss. In order to find better materials for these cell-interconnect, the researchers turned to conducting polymers; which are getting very popular.
Conducting polymers can be made thin, transparent and flexible; perfect for solar cells as they require less material and lower costs. However, this theory required a new process to create the cells. The Purdue research purportedly is the first time lasers were used to successfully to create the interconnects. Yung Shin, professor at Purdue who led the study said, “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 ultra-fast lasers are able to create pulses lasting only picoseconds without overheating the material, creating silky smooth and sharp channels. “It creates very clean microchannels on the surface of each layer. You can do this at very high speed, meters per second, which is not possible with a mechanical scribe. This is very tricky because the laser must be precisely controlled so that it penetrates only one layer of the thin film at a time, and the layers are extremely thin. You can do that with this kind of laser because you have a very precise control of the depth, to about 10 to 20 nanometers,” said Yung Shin.
Expect to see this research make its way into the private sector in order to increase thin film cell production from 20% today to 31% in just two years.
The team has published a paper on their work at the 2011 NSF Engineering Research and Innovation Conference in January.