A tale of two wafers: Both begin as 99.9999999 percent pure silicon, one of the basic ingredients in desert sand. A furnace melts the silicon and controls the cooling and growing of a mono-crystalline cylindrical ingot which is then sliced into standard 100 to 300mm (4 to 7.5 inch) wafers. Infinitesimal quantities of doping materials are added to change the wafer into a semiconductor with the correct properties to become either a microchip or a photovoltaic solar cell. From this point these two types of wafers go their separate ways and give little indication of their common roots. But now a company named Sol Chip of Haifa Israel intends to combine these two silicon-based technologies to make solar-powered microchips.
In 1981 I connected a photovoltaic solar cell to a pocket calculator. I stood on a chair, held it up to the classroom’s florescent light and it worked! My friend Fernando laughed at me and I didn’t get a patent. Within two years nearly every pocket calculator was powered by photovoltaics and ambient light. Thirty-one years later microchips are in RFID tags for livestock, medical devices, utility monitoring equipment, cars, satellites, remote sensing buoys, price tags, toys, security alarms… It seems that microchips are everywhere!
Given what happened to pocket calculators, I would have expected that every laptop, phone and flying car would be powered by solar energy by now. But while microchips advanced beyond my wildest dreams, photovoltaics languished in the disco era.
Perhaps I’m being harsh, photovoltaics are advancing, albeit at a snail’s pace. For example photovoltaic cost has fallen from about $100 per watt in 1970 to about $1 per watt in 2012. But during the same time, the cost of a microchip transistor dropped from one dollar to less than 1 millionth of a dollar. Perhaps there hasn’t been enough collaboration between the photovoltaic wafer engineers and those hot-shot microchip wafer engineers.
Fortunately that is about to change. Sol Chip raised one million dollars to develop their solar chip technology.
Their idea is to create light-powered chips for these small ubiquitous wireless devices. The chips will have windows on top like some EEPROM memory chips do. But these windows illuminate the photovoltaic device and power the chip.
This will allow small devices to run indefinitely without replacing and disposing of those silly lithium batteries. That’s good for the environment. Sol Chip’s idea sounds simple but if you’ve owned several hundred RFID-tagged sheep or a beluga whale transponder, you’d appreciate not having to replace their batteries every year.