Hydrogen Annealing Increases Efficiency Of Solar Cells

With this advancement, hydrogen annealing could pave the way for more efficient, sustainable solar energy solutions, bringing affordable green energy closer to reality.

Photovoltaic (PV) technology continues to evolve as researchers seek sustainable materials that enhance efficiency while lowering costs. A promising candidate is wide-bandgap kesterite Cu₂ZnSnS₄ (CZTS), a non-toxic semiconductor made from earth-abundant elements. Unlike silicon, the dominant material in solar cells, CZTS offers a more sustainable and cost-effective alternative. However, its efficiency has lagged behind, with a maximum power conversion efficiency (PCE) of just 11%, primarily due to carrier recombination, where generated charge carriers recombine before producing electricity.

Researchers at the University of New South Wales (UNSW), Sydney, have developed a technique to mitigate this issue using hydrogen annealing. Their study demonstrates how this process improves carrier collection by redistributing oxygen and sodium within CZTS layers, enhancing overall performance.

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Hydrogen annealing involves heating the solar cell material in a hydrogen-containing environment. This process helps redistribute sodium and passivate defects, especially near the absorber surface, significantly improving carrier transport. The technique resulted in a record CZTS efficiency of 11.4% in a cadmium-free solar cell.

Beyond CZTS, the method has also shown promise in other thin-film solar materials like copper indium gallium selenide (CIGS), demonstrating its broader applicability. “This breakthrough strengthens CZTS’s role as a top cell material in tandem architectures, enabling better silicon integration and broader solar spectrum utilization,” Sun added.

The researchers now aim to push CZTS efficiency beyond 15% while maintaining its economic and environmental advantages. “Further refining the hydrogen annealing process and exploring new optimization techniques will be key to making CZTS a viable alternative for next-generation solar technologies,” said Sun.

“Our work was driven by the need for an eco-friendly, low-cost material for next-generation solar cells,” said Kaiwen Sun, senior author of the study. “CZTS is an excellent candidate for tandem solar cells due to its tunable bandgap, stability, and sustainability. However, improving carrier collection efficiency has been a challenge.”