High-efficiency silicon minMIS solar cells—Design and experimental results

Grating minority-carrier Metal-Insulator-Semiconductor (minMIS) solar cells have been fabricated on a range of Czochvalski (CZ) and float-zone (FZ) substrates. The most efficient cells result when the semiconductor surface between the grating lines is inverted. This can be achieved for p-type substrates with minimal interference to light transmission using the fixed positive charge in antireflection (AR) coating materials such as SiO. To characterize the measured short-circuit current of grating cells, the concept of an effective minority-carrier collection distance Δ is introduced. Δ is shown to be proportional to the inverse square root of input light power. Knowing Δ, an appropriate grating spacing can be determined. Record open-circuit voltages of 655 mV (AM0, 25°C) for 0.1-Ω. cm FZ substrates have been achieved. AM1 active area efficiencies of 17.6 percent for polished substrates and 17.4 percent for textured substrates have been measured.