Electrical engineering

Nanotechnology

Organic chemistry

Energy conversion efficiency

Crystalline silicon

Boron

Photovoltaics

Crystallography

Engineering

Wafer

Chemistry

Materials science

Amorphous silicon

Photovoltaic system

Solar cell

Silicon

Amorphous solid

Polymer solar cell

Optoelectronics

Doping

Nanocrystalline silicon

Nature Energy

Recent achievements in amorphous/crystalline silicon heterojunction (SHJ) solar cells and perovskite/SHJ tandem solar cells place hydrogenated amorphous silicon (a-Si:H) at the forefront of photovoltaics. Due to the extremely low effective doping efficiency of trivalent boron in amorphous tetravalent silicon, light harvesting of aforementioned devices is limited by their fill factors (FFs), a direct metric of the charge carrier transport. It is challenging but crucial to develop highly conductive doped a-Si:H with minimal FF losses. Here we report that light soaking can efficiently boost the dark conductance of boron-doped a-Si:H thin films. Light induces diffusion and hopping of weakly bound hydrogen atoms, which activates boron doping. The effect is reversible and the dark conductivity decreases over time when the solar cell is no longer illuminated. By implementing this effect to SHJ solar cells, we achieved a certified total-area power conversion efficiency of 25.18% with a FF of 85.42% on a 244.63 cm 2 wafer.

Light-induced activation of boron doping in hydrogenated amorphous silicon for over 25% efficiency silicon solar cells