Drawing the Most Power From Low-Cost Single-Well 1-mm2 CMOS Photovoltaic Cells

Abstract

Photovoltaic (PV) cells can generate 100× more power from light than other transducers can from motion, radiation, and heat. Although custom multijunction nonsilicon and multiwell complementary metal–oxide–semiconductor (CMOS) cells output more power, single-well process technologies cost less. Amorphous cells cost even less but output less power. However, with only a small window of light available, tiny CMOS cells output little. This brief explores and proposes open-terminal single-well CMOS PV cell configurations that output more power than competing low-cost CMOS cells in literature. Measurements with 0.35- $\mu\text{m}$ $1\times 1\text{-mm}^{2}$ single-well CMOS cells show that deeper and lighter doped junctions generate higher power than shallower junctions, and double-junction configurations output even higher power. This is why sunlight on N+ in P substrate and N well in P substrate cells outputs 6 and 98 $\mu\text{W}$ and on shorted and open-terminal P+ in N well in P substrate structures outputs 132 $\mu\text{W}$ . Opening the P+ terminal outputs even more power because P+ metal, which blocks light, is no longer necessary.