In a step towards self-powered chips, Taiwan's National Nano Device Laboratories revealed a two-sided solar cell integrated with thin-film transistors (TFTs).
One side is a silicon solar cell made on a silicon substrate.
Deposited on the other side of the substrate is a solar cell made from CIGS (CuInGaSe2), plus TFTs made from the same material.
"The novel manufacturing process avoids the use of environmentally harmful cadmium, as well as sodium typically found in CIGS solar-cells, but at the expense of cell efficiency," said IEEE. "To compensate, the CIGS layer was deposited on a textured surface, bringing the CIGS cell conversion efficiency up to 11%."
The integrated TFTs achieved what is claimed to be record performance for CIGS technology - demonstrating hole mobility of 0.22cm2/V.
"The relatively low-temperature [400-500°C] and sodium-free manufacturing process could mean this CIGS-fabrication technique may be compatible with CMOS processing," said the IEEE.
The images show a 150mm CIGS solar cell made on the back of a silicon solar cell, and the same thing with integrated CIGS TFTs.
IEDM paper 36.5:
Bifacial CIGS/Si solar cells by Cd-free and sodium-free green process integrated with CIGS TFTs