Solar powered microchips put batteries in the shade

In a new, more efficient approach to solar powered microelectronics, researchers have produced a microchip which directly integrates photovoltaic cells. While harnessing sunlight to power microelectronics isn't new, conventional set-ups use a separate solar cell and battery. What sets this device apart from is that high-efficiency solar cells are placed straight onto the electronics, producing self-sufficient, low-power devices which are highly suitable for industrial serial production and can even operate indoors.
The autonomous microsystem was developed by the Semiconductor Components group at the University of Twente's MESA+ Institute for Nanotechnology led by Professor Jurriaan Schmitz. The researchers collaborated with colleagues from Nankai University in Tianjin, China and the Debye Institute of Utrecht University. The research was made possible by the STW Technology Foundation.
Instead of manufacturing the solar cell separately, the design sees the chip used as a base and the solar cell applied to it layer by layer. According to the UT release, this results in a more efficient production process, uses fewer materials and ultimately performs better.
The production process has not been trouble-free with the researchers finding that the fragile electronics can easily be damaged. For this reason it was decided to use amorphous silicon or CIGS (copper - indium - gallium – selenide) solar cells. The manufacturing of these cells does not influence the electronics, and these types of solar cells also produce sufficient power to allow the microprocessors to operate in low-light or indoors. There is a catch though – the chip's energy use must be well below 1 milliwatt.
Tests have shown that the electronics and the solar cells function properly, and the manufacturing process is also highly suitable for industrial serial production with the use of standard processes.
The paper Above-CMOS a-Si and CIGS Solar Cells for Powering Autonomous Microsystems by J. Lu, W. Liu, C.H.M. van der Werf, A.Y. Kovalgin, Y. Sun, R.E.I. Schropp and J. Schmitz was presented at the International Electron Device Meeting in San Francisco in December.