Self powering smartphones on the way?

A team led by Professor Arokia Nathan has built a prototype device made up of thin-film hydrogenated amorphous silicon that sits within a phone's screen to harness wasted light and turn it into electricity. The solar array works in conjunction with a thin-film supercapacitor and a thin-film transistor circuit, which is designed to smooth out voltage spikes. "The combination of photovoltaics, transistors, and a supercapacitor yielded a system with an average efficiency of 11% and peak efficiency of 18%," said Prof Nathan. "If the PV array converts 5% of ambient light to electricity, the energy harvesting system can generate as much as 165microwatts per square centimetre under the right lighting conditions. "For a typical 3.7in smartphone screen, that equates to a maximum power output of 5milliwatts, which is quite useful power." While useful, Nathan admits there is still more work to be done to get the device ready for the consumer. He believes other energy scavenging schemes, such as MEMS based kinetic energy harvesting, could contribute to further improvements.