“You might probably have noticed that recent solar news have been populated by press releases from different manufacturers stating that they would either start or increase their manufacturing capacity in PERC cell technology in order to produce high power and high efficiency solar panels. Some of them may switch complete manufacturing capacities to PERC technology or achieved High efficiency records. To help you weather the flow of information, discern the right from the sales-pitch, we prepared this summary of the key information to know about the technology.” 1. What does PERC mean? Literally, it stands for Passivated Emitter and Rear Cell. You also find the term Passivated Emitter and Rear Contact. 2. What is it? PERC cell technology defines a solar cell architecture that differs from the standard cell architecture that has been in use for three decades and that is usually featured in all photovoltaic manuals. As of today, the vast majority of crystalline solar cells produced follow the above structure. From top to rear: – screen printed silver paste to form the contacts – Anti Reflective Coating – phosphorous diffused, boron doped silicon wafers that form the P-N junction – aluminum Back Surface Field (Al-BSF) – screen printed aluminum paste The objective of scientists being to get the most of electrons out of the solar cells, the PERC architecture essentially enables to improve light capture near the rear surface and to optimize electrons capture. 3. PERC and PERC? Under the acronym PERC, we actually also find the solar cells technologies named PERL, PERT, PERF. Even if initially not considered in the nomenclature of PERC, they are now usually considered as being part of the same family 4. What’s the interest of the technology? The main advantage of the PERC cell structure is that it enables manufacturers to achieve higher efficiencies than with standard solar cells which are reaching their physical limits. With the current state of the technology, it is possible to achieve up to 1% absolute gain in efficiency. While there are more steps in the manufacturing process, the gain in efficiency enables costs decrease, also at the system level. We should always keep in mind that the Holy Grail is to improve efficiency while reducing costs at the same time. And solar cell efficiency improvement is a contributor to the reduction of costs. So this cell architecture is considered like presenting one of the best potential for producing high efficiency solar panels at competitive prices. 5. Is it new? The PERC architecture is actually not new at all. First evocation of the technology traces back at the University of New South Wales in Australia in 1983 and the first paper has been published in 1989. Because this concept of cell offered the best potential to reach high efficiency, the UNSW used it to achieve its multiple world records of efficiency that it brought close to 25%. The two others competing technologies were the Back Contact technology, popularized by Sunpower, and the HIT technology commercialized by Panasonic. 6. Why now? It is interesting to underline that the standard solar cell architecture has been in use since the middle of the 80’s. Since then, the technology went through incremental improvement, with better pastes to form front contacts, thinner contact fingers, optimized anti reflective coating… It took almost 30 years to the industry to almost catch up with the efficiencies achieved at the research level. The following graph sums up the historic quest of the solar industry to improve its technology. 7. Does PERC technology intrinsically feature better weak light performance? In parallel to the development of the PERC technology, we have seen appearing on datasheets arguments related to improved performance under weak light. It is then legitimate to wonder if those two facts are related. While it is true that you will find PERC based modules with improved weak light performance, it has nothing to do intrinsically with the PERC cell technology. All the cell technologies have the potential to feature an improved performance under low light conditions, and we will address this topic in a next blog post. Sources [1]: A.W.Blakers, A.Wang, A.M.Milne, J.Zhao, M.A.Green, 22.8%Efficient Silicon Solar Cell, Appl. Phys. Lett. 55 (1989) 1363–1365. [2]: Zhao J; Wang A; Keevers MJ; Green MA, 2000, High efficiency PERT cells on SEH p-type Si substrates and PERT cells on SHE n-type Si substrates [3]: M.A. Green, The Passivated Emitter and Rear Cell(PERC):From conception to mass production, Solar Energy Materials & Solar Cells 143 (2015) 190–197 [4]: M.A. Green, Forty Years of Photovoltaic Research at UNSW, Journal and Proceedings of the Royal Society of New South Wales, vol. 148, nos. 455 & 456, pp. 2-14