Light trapping in silicon nanowire solar cells

Area of Science:

• Materials Science
• Nanotechnology
• Renewable Energy

Background:

• Thin-film solar cells offer cost reduction potential but suffer from short optical path lengths.
• Effective light trapping is crucial for thin-film solar cells to overcome limited absorption.
• Semiconducting nanowire arrays show promise for reducing reflection losses in solar applications.

Purpose of the Study:

• To measure the light-trapping properties of ordered semiconducting nanowire arrays.
• To investigate the impact of nanowire arrays on the optical path length of solar radiation.
• To evaluate the performance of silicon nanowire arrays in thin-film solar devices.

Main Methods:

• Utilized optical transmission and photocurrent measurements on thin silicon films.
• Fabricated ordered arrays of silicon nanowires on thin silicon films.
• Varied silicon film thickness and nanowire length to study their effects.

Main Results:

• Demonstrated a light-trapping path length enhancement factor of up to 73 in silicon nanowire arrays.
• Achieved light trapping exceeding the theoretical Lambertian limit.
• Observed enhanced absorption dominating surface recombination in 8 µm thick silicon films, leading to efficiencies over 5%.

Conclusions:

• Ordered silicon nanowire arrays provide superior light-trapping capabilities for thin-film solar cells.
• Nanowire geometry can be optimized to balance enhanced absorption and surface recombination.
• This approach offers a viable path towards more efficient and cost-effective thin-film solar power.