New solar cell survives severe shading stress while retaining 97% efficiency

Researchers at The Hong Kong Polytechnic University (PolyU) have developed a perovskite-organic tandem solar cell that remains highly efficient under partial shading.

The cells retained more than 90% of their initial efficiency after exposure to a severe -40 V reverse-bias voltage, which can permanently damage conventional thin-film solar cells.

Why Shading Damages Solar Cells

Partial shading from clouds, trees, buildings, or birds can force shaded cells into reverse bias, reducing power output and causing long-term degradation.

Researchers identified deep trap states in the bulk heterojunction as a key cause of this damage. These defects trap electrical charges and increase the risk of irreversible degradation.

By modifying the donor-acceptor structure and suppressing the formation of defect-rich clusters, the team significantly reduced these trap states. The resulting organic solar cells withstood breakdown voltages above -35 V.

97% Efficiency After 2,000 Hours

The improved organic cells also helped protect the perovskite layer in n-i-p tandem devices by suppressing reverse tunneling.

After exposure to -40 V, the tandem cells retained more than 90% of their initial efficiency. At –20 V for 12 hours, they retained about 90%, while after 2,000 hours at -4.5 V, they still maintained 97% of their original efficiency.

The tandem devices also achieved power-conversion efficiencies above 26%, combining high efficiency with significantly improved resistance to shading-related stress.

The results, published in Nature Materials, could help make next-generation thin-film solar modules more durable and reliable in real-world conditions.