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JUNE 2020 I PCB007 MAGAZINE 85 ing taxes, but the consistent revenue stream of future military aerospace electronics is a close third. PCB007 Mike Hill is president of MIL-Q-Con- sulting LLC. He has been in the PWB fabrication industry for over 40 years. During that time, he participated in specification writing for both IPC and the military. Past employers include ViaSystems, Colonial Circuits, and DDi. To read past columns or contact Hill, click here or email Milqconsulting@outlook.com. This last phase will take 30–60 days, and adding the times of all the seven phases results in a range of 5–12 months to complete the cer- tification. Summary Certification to MIL-PRF-31032 offers a wid- er range of the PWB military aerospace sector than just the parts built to IPC-6012. Certifi- cation, of course, does not come easy and re- quires some hard, dedicated work. However, as they always say, "No pain, no gain." Life certainties are said to be only death and pay- Photovoltaics, or solar cells, work by absorbing sun- light to produce clean electricity. But photovoltaics can absorb only a fraction of the solar spectrum, which lim- its their efficiencies. The typical efficiency of a solar pan- el is 18–20%. Researchers have started developing "tandem" solar cells by stacking two solar cells, absorbing complemen- tary parts of the solar spectrum, on top of each other. The most promising of these tandem solar cells is a perovskite device stacked on a silicon device. Perovskites absorb visible light, whereas silicon ab- sorbs near-infrared light. A perovskite-silicon tandem so- lar cell could realistically achieve 35% efficiency within the next decade. The challenge with these tandem solar cells is that the electrode covering the perovskite solar cell needs to be transparent, and this transparent electrode is deposited using high-energy processes that damage the perovskite. A team of researchers from Cambridge's Department of Materials Science, working with Imperial College London and the Solar Energy Research Institute of Singapore, de- veloped a method to "print" a protective coating of cop- per oxide over the perovskite device. Only a 3-nanome- ter coating is sufficient to prevent any damage to the perovskite after depositing the transparent top electrode. These devices reach 24.4% efficiency in tandem with a silicon cell. (Source: University of Cambridge) Printed Coatings Enable More Efficient Solar Cells