Coming: Combo energy scavenger, electronics chips

Coming: Combo energy scavenger, electronics chips

It looks as though the next generation of energy scavengers could combine scavenging mechanisms such as solar cells and vibration sensors with electronics, all on the same silicon chip. This is one of the conclusions that might be drawn from the recently completed International Electron Device Meeting in San Francisco, where researchers from several institutions reported progress on devising such combo devices.

One example is work done at the University of Michigan where researchers fabricated a CMOS-compatible piezoelectric inertial power generator. The wafer-level fabrication process integrates bulk piezoelectric ceramic on silicon by aligned low-temperature solder-bonding and thinning to 5 to 100 µm while conserving bulk properties. Researchers say the 12.1-mm3 harvester generates 0.15 µw from input acceleration of 0.1 g at 263 Hz and 10.2 µw from 2 g at 252 Hz.

Researchers at Fujitsu Laboratories, Ltd.described a hybrid energy harvesting device generating power either via photovoltaic or thermoelectric means. The device was fabricated using organic materials.

Finally, researchers hailing from the University of Twente, Nankai University, and Debye Institute discussed amorphous-silicon and CIGS solar cells they grew on chips from two CMOS generations. The efficiency of the Amorphous-silicon (a-Si) solar cells reaches 5.2%, copper-indium-gallium-selenide (CIGS) cells 7.1%. The CMOS electronics underneath the PV cells worked just fine, say researchers. The main integration issues: adhesion, surface topography, metal ion contamination, process temperature, and mechanical stress can be resolved while maintaining standard photovoltaic processing.

However, the chip's energy use must be well below 1 mW, say the researchers.

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