Above-CMOS a-Si and CIGS solar cells for powering autonomous microsystems

Abstract

Two types of solar cells are successfully grown on chips from two CMOS generations. The efficiency of amorphous-silicon (a-Si) solar cells reaches 5.2%, copperindium-gallium-selenide (CIGS) cells 7.1%. CMOS functionality is unaffected. The main integration issues: adhesion, surface topography, metal ion contamination, process temperature, and mechanical stress can be resolved while maintaining standard photovoltaic processing.

Solar cells on CMOS chips as energy harvesters : integration and CMOS compatibility

“…All efficiencies on this Cu-PCM chip from 2 nd Run are higher than the best CIGS efficiency (7.1%) obtained without the Ti adhesion layer from the 1 st Run, as reported in [146]. Further, the efficiency gap between the CMOS chip and the glass reference has decreased from 1~5% [146] to 0.9% in the new experiments.…”

“…Further, the efficiency gap between the CMOS chip and the glass reference has decreased from 1~5% [146] to 0.9% in the new experiments.…”

“…The integration of a-Si solar cells on Timepix and Cu-PCM chips showed no direct impact of roughness on the solar cell efficiency during the 1 st Run experiment [146], but the Ringo chips exhibited even higher topography (see Fig. 4.4).…”

“…5.9, we see in the 400 ºC and 425 ºC fabricated CIGS solar cells an indication of the existence of (In 1-x Ga x ) 2 Se 3 . This is commonly attributed to a lack of thermal activation energy, and may result in a reduced solar cell efficiency may result [146,193]. The <112> peak at 450 ºC shifts to lower number compared to the same peaks at other temperatures.…”

“…After the 1 st -Run experiment, as reported in work [146], three process adaptations were made in the 2 nd -Run experiment: the p-type Si layer is now microcrystalline rather than amorphous; the realized samples were optionally annealed at 140 °C in N 2 ambient for 16 hours; and the optional Au grid mentioned in [146] has not been employed for the new experiments, at the expense of solar cell efficiency, for a better comparison. In addition, the active area of the realized solar cells in the 2 nd Run is 0.16 cm 2 for all the samples.…”